LU Definition Updates fails for NAV 21.7.0.11

I know, perhaps not the safest option, however, to stay with Norton I have no choice!  So I use NAV 21.7.0.11 for two legacy computers with SSE only CPUs.  Until recently, I had no problems to get updates automatically and via LU.

However, now I can't update the NAV Virus and IPS definitions:

I did a clean reinstall of NAV 21.7.0.11, but, no change.  Besides, the problem happens on both the legacy computers, so it's not a single incident.  As I have done in the past, I went here to download a full size offline definition file:

https://www.symantec.com/security_response/definitions/download/detail.jsp?gid=n95

Regrettably, all recent files fail to update.  I had to go back to 20170124-001-v5i32.exe to be successful.  What's up?  Any ideas?  Remember, updating to NAV 22.x.x is not an option as for that I need SSE2 based CPUs.  Thanks.