Norton Identity Safe 2015.7.0.68 (IE) does not open

I use Norton Security 22.7.0.76 with Norton Identity Safe v2015.7.0.68 in IE browser (Win10). Till this morning all went fine - then I got notice to reboot Notebook in order to update Norton. Since then I have a problem to open my Identity Safe:

First I get a window "First steps" with the request to login to my Norton Accoount in order to create a new Safe - but I already use one since years. Still I login. I enter my email address and password. If I use a wrong pw I get message, that address+pw are wrong. If I use the correct pw, there is no such message (obviously) but the window just closes, and I am back with the First Steps window. So I repeat this several times, but no change.

So I login directly via IE to my Norton Account via email address and pw --> works fine

So I login via IE to my Identity Safe vault with the vault password --> all is fine.

But opening the vault in IE via Norton add-on bar, still offers me only the First Steps window, and logging in via my correct email address and pw just shows no reaction at all.

HELP!