P: File extension (ex. jpg) not changing during format change after upgrade to macOS 10.15 Catalina

Wrong. This is not it. Try open a .jpg file. Add a layer and try to save it as .jpg It does't work.  Aka File extension (ex. jpg) not changing during format change after upgrade to macOS 10.15 Catalina

Hi Axel, I think i was having a different issue from other folks. My issue was with files created before the upgrade to the new iOS. When I would open and try to save them (manually or otherwise), they would not open again. I just found that if I manually saved, AND turned off Maximize Compatibility, then I was able to reopen files. 

ok! i found a work around: when on this screen, unclick Maximize Compatibility and it works! 

That way this complain os about, you have to save .jpg, .psd etc manually.

Hmm, that doesn't seem to be the issue on my end. I'm saving it as a PSD, but when I go to reopen the file it does not open and gives me that error. 

You are accidentally saving files with the wrong file extension because an issue in Catalina. See the Save As section here: https://helpx.adobe.com/photoshop/kb/photoshop-and-macos-catalina.html#Filenamingoptionsdontworkcorr...

" Could not complete your request because it is not a valid Photoshop document."

I'm getting this error when trying to open Photoshop documents in newly updated iOS Catalina

And who would have ever thought that installing Catalina would cause this problem with Photoshop?  Where would one even begin to check for this type of compatibility issue?  I update when the new operating systems come out for security reasons as well as bug fixes regarding current issues, so who knows what will happen after installation of a new system...only the tech gurus can fix these things.

Johan -- as far as I know, my DAP program is 64 bit compatible, but it seems to be the WINE wrapping that's causing the problem.  Who can determine all of this on every piece of software one is running before updating??  I like to keep my computer up to date for security reasons, so I always install the new operating systems when they come out...and I don't like to be thought of as being stupid for doing this -- who can keep up with all of the rapid-fire changes in technology unless you're in the industry that's creating them?  It should be the job of the software developers to keep their products updated, not mine -- they're the ones making money, and I'm the one spending it.  DAP is 64 bit, but WINE is not, so the conflict is there.  DAP is trying to make their program useable on a Mac, so good for them!  It works well, and I like the software and will find a way to use it if I have to boot from Mojave installed on an external disk until the update comes!  HAVE A GREAT DAY!

No, you will have to wait for an update. This is why it is so important to first read the info on compatibility issues and then decide if you upgrade your OS or wait till these kind of problems are solved.