Trying to export a still frame from the sequence, but it's not writing the file. It appears to complete ok, but the .jpg file does not appear in the export-to folder (Windows 10). If I re-try the exact same export, to the same folder, with the same filename, it appears to complete again (without saying the file already exists), but again... no file. I tried different folders and filenames, same result.
Then I created a test file in a folder, and tried to export a frame to that filename and folder. Got the "File already exists. Overwrite?" msg, and said "yes" to overwrite it. That appeared to complete ok, but the result was that the file was deleted from the folder, not overwritten. Any suggestions?
It sounds like there could be an issue with the folder's write permissions. Have you tried exporting straight to your Desktop as a test? Also, are you by any chance running Premiere as an Admin? I don't mean if your user account is an Admin, but are you explicitly running the program with elevated permissions?
I talked with a support person. He had me import the project into a new one and try again. That worked. I asked him what the real problem was and why that worked, and his answer was "sometimes there's problems with meta data". I thought that was a rather poor answer, but it's all he had to offer; at least it worked.
It may sound like a poor answer, but this is actually a common troubleshooting step and solution. Every item in a project has an internal ID assigned to it and sometimes (there are lots of reasons, but I'm not a developer who could give you a more technical answer) this internal project data gets corrupted and causes all sorts of wacky issues. This happens in After Effect too and the solution is to create a new project and import your previous project into it.
Essentially, this creates a clean environment for your project and keeps the good stuff from your previous project while ignoring the bad stuff.