Answered
Hi
Good news: the issue is resolved. The cause was my security software (Intego), which had pending updates and was interfering with the Photoshop update in Creative Cloud. Once Intego was fully up to date, I was able to install Photoshop successfully, and it now launches normally.
For anyone running into the same "damaged or incomplete" message with a stuck update, it's worth checking that your antivirus/firewall is up to date, and temporarily pausing it during the installation if needed.
Thanks again for your help!
