The last two times, after updating PS 25.8 and 25.9, I can't start PS

Try a manual reset of your Photoshop preferences - here's how to do that:

• https://helpx.adobe.com/photoshop/using/preferences.html#Manually

(Be sure to make a backup of your settings first!)

If that fails, try a clean install next by using the 'Creative Cloud Cleaner tool' to fully remove your current installation and possible leftovers from earlier ones:

• https://helpx.adobe.com/creative-cloud/kb/cc-cleaner-tool-installation-problems.html

Afterwards, head into the 'Creative Cloud desktop client' and install Photoshop like you normally would.