We have been using the function Export > Save To Image > JPEG for at least 10 years in Acrobat, 4 users, everyday. Since february 2 of our users got this problem and now last month the other 2 also got it. So this problem can be realeated to Windows Update or Adobe Updates
When saving to JPEG to a network-drive (eg. S:\FOLDER\ ) a temp file is createad and disapears. And no JPEG can be found in the folder. In acrobat you can see the loadbar for a quick secound.
The same problem if you save to the correct URI of the server (eg. \\SERVERHOSTNAME\Folder\ )
If you save the file to C:\FOLDER\ the processes works without any problem
And now the realy strange part. If you save as PNG to the networkdrive, then it works. The file appears in the correct folder