Inspiron 15R SE 7520

Hi. My 10-year-old, originally Win 8 laptop got upgraded to Win 10 years ago and has run happily since. A year or so ago I treated it to a new SSD which may have been a mistake. Recent issues made me look for the options to refresh or reinstall Windows,  and I'm now told that I no longer have the files to create a recovery drive and cannot refresh or install anything.  That partition may have been corrupted on the SSD. (SFC tells me there are no issues with anything!)

The problems are that I am currently unable to use Windows Update or Windows Defender - I'd suspect a virus, but have run several online virus checks - and none of the fixes I've been able to find from MS correct those issues.

SupportAssist is installed,  but when selected it won't activate - it suggests a restart and try again.

I have checked for other system issues and run the hardware tests but everything is fine - except Win 10 is still compromised.  Anyone any suggestions for what I could try next?

(EDIT:  I also have the 8950 desktop which I can't remove from this post!!)