I am experiencing the same problem. We have 2 company files and both are having the issue. QB tech support tried helping and suggested running the Verify option to check the file. Ran on one of the files and found no problems and still will not back up. Only starts a tmp file. I have set time so I can actually watch the backup which runs, creates the tmp file and that's it. Whole process took about 5 seconds. We went from QB Enterprise 2016 to 2019. Have no issues running manually. This appears to have something to do with the 2019 Version.