I was out all day and I had just got back when I read Imacri's "bad news" alert for the re-incidence of the problem. As it seems, the issue has been resolved in light speed fashion by the "dev team" and that's great news...
So, the same way criticism is usually voiced when things go less than good, it's only fair to give a word of appreciation to both the team for having taken care of the problem in record time and to Tony for immediately bringing the news.
Way to go...
Thanks!
Thanks @lmacri. It looks like this is was solved pretty quickly, and in talking with the dev team, is a separate issue from the one seen last weekend. I appreciate the update though, and I'm glad it's working well for you now.
Bad news. I just had a few more of these Error 503 messages while I was trying to post in the forum this afternoon but the text is slightly different today i.e., "Error 503 Backend is unhealthy" (and not "Error 503 All backends failed or unhealthy").
The first error came when I tried to post a reply in Dave1776's thread Secure Connection Failed at https://community.norton.com/en/forums/secure-connection-failed-0. I don't know if it's significant, but this first composed message included a hyperlink that I copied and pasted from an older thread. When I clicked the "Save" button to try to post my reply the Error 503 message was displayed and my reply never appeared in the thread. I also noticed that I was logged out of the forum after I hit the "Save" button.
I immediately received a second Error 503 message when I clicked the "Log In" link to log back into the forum:
I waited a few minutes and was eventually able to log into the forum and post my reply.
------------
32-bit Vista Home Premium SP2 * Firefox v46.0.1 * NIS v21.7.0.11 * MBAM Premium v2.2.1
OK, guys. You were very gracious and admirably self-deprecating. Here is what I think:
Tony is certainly one good possibility, although -- without taking away any merit he rightly deserves -- he acted here in his quality of a Symantec representative and, as such, so acted the development "crew", who actually made, tested and applied the fixes... Tony also brought us the good news...They all do deserve our appreciation and they may also receive other performance rewards as a result of a job well done -- and this is, after all, an inherent part of their jobs well done... Nothing new here, all this is just fine and fair.
But what about those of you who are helping here, gratis, just for the sake of helping?... Let's be clear, you people invest your dedication, your time and your patience, and the only reward you can get, AFAIK, besides your own inner satisfaction, may be just the simple gestures of recognition from the part of those who are helped. We are talking here about the most basic gestures of gratitude, just like as if saying -- "Thank you, and here is a tiny token of my deep appreciation..."
Honestly, this is how I see it. But considering that in this case, and to the extent that we all had the same issue and depended on Symantec to have it resolved, I will give it to Tony on your recommendation, on his own merit and on the merits of those from the development team who got involved...
Cheers and many thanks to ALL.
Certainly Tony and the crew.
IMO, to Tony Weiss https://community.norton.com/en/comment/6989931#comment-6989931
It appears that we can now definitively say the issue is gone for good, which obliges me to ask the following and last question...
-- I opened this thread with the indication that a solution was required; I understand there have been more than one individual involved (possibly in varying degrees) in the quest for a response from Symantec's development team; I wished to register the solution "award" to all who were actively involved but, unfortunately, I can give it to only one single person, and I want to be fair.
The question, then, is: To whom should I send the "Solved" award?...
Recommendations are very welcome!
I believe you too, that's for sure ...But I realize I'm off the loop... My own fault, though... Never been too good at reading the cards... 
LinYu
There's more too all this than we know ....
Hi Tony,
Many thanks for bringing out the good news!
After receiving an email message announcing your post, I have tried a number of times to different links and the truth is... No issue encountered.
As you are certainly aware, this was an "On-and-Off" kind of situation, so with this in mind, I would say that the problem may have been finally fixed. I hope that is definitely the case. Not a major issue, as I said before, but a sizable nuisance...
Thanks again and have a good day.
Hi folks, our dev team has made some fixes - can you tell me if you're still seeing this issue? If so, please post a screenshot of the error, and the URL you were trying to access. Thanks.
OK, Hugh, I understand you are "too" in the same straights as I am... Let me, then, joke a bit and guess a bit so that we can dissipate or shoo out some stress... 
So, as I see it, it's "You too", "Me too"... and "who else too"?...
Whatever happened to all others? Or are they in different "triangulation" servers" ?...
For fairness' sake, are we all equally "too" or are some of us more "too" than others" ?... 
LinYu
Me too!
Yes, indeed... I fully agree.
Thanks!
LinYu2:
... Is it impolite to say that that's what Gurus are for?...
No, not at all... maybe we could say "that that's what Gurus are also for?"
Have a great day too.
I had received the error earlier today, but now, right after finishing my previous post, I clicked on Rainbow_2's message link and was greeted by the now infamous 503...
Well, let's give'm some time. They may be experiencing a greater hardship than ours which is relatively minor. Or the "renegades" may be too stubborn to be easily convinced to lay arms...
Thanks.
Great! And thanks for your involvement. Is it impolite to say that that's what Gurus are for?...
Now, like you say, in the "battle front" I can still observe a few sporadic shots... But I admit they may come from a few renegades left behind by the retreating enemy... 
In truth, I agree with you on that the incidence of the error is much more infrequent than during the weekend. So, to remain on a positive note, I hope the problem has been identified and taken care of for good.
Thanks again and have a great day.
It's fixed!
LinYu2
... I meant to suggest a good word to, say, a friendly ear at Symantec...
Don't worry -- that's been done by gurus in our own discussions over the weekend and several of Norton management notified.
If as we all seem to think, "it's not us it's them" be certain that it must be causing them more problems than we experience so it will get fixed! There's less staff at weekends so today is catchup time and it will get a reaction.
My links here worked first time this morning but some from yesterday gave the 503 error! That's odd. But I only had two email advisories from Norton this morning so it may just be chance as it was previously.