I had this issue and my resolution was found here:

https://blog.workinghardinit.work/tag/mismatch-in-virtual-sizes-the-parent-virtual-hard-disk-and-differencing-disk/

As long as that link still works you should be fine. If not I’ll have to write my own version of the article. In essence, you probably have a checkpoint enabled on the VM and there is a failed relationship between the differencing disk file and the disk file for that VM if it fails to start with error 32791.