SupportAssist will not install

As suggested by Imacri I am posting my machine details for better help and support on this problem. I have used Dell SupportAssist since the machine was new 3 years ago, but SA has suddenly stopped working today without warning. I have followed all the advice I can find, uninstalled SA and rebooted etc etc. The machine last ran SA successfully about a week ago, so all drivers etc should be current.

Dell XPS13 9370 i5

Windows 11 Pro

Bios 1.21.0 (6/7/22)

The issue started when I tried to run SA earlier. It said it wanted to update the SA version. Ran the update and got the failure message asking for reboot. Then went through the whole thing of uninstalling SA, rebooting, retrying the install using the SA link on the Support Page, all to no avail.

Any help would be welcome!

thanks