I can't speak for them for sure, but they don't do refunds. I think we stand a much better chance to get whatever caused this to happen (as I said, I was able to get it to happen to me) fixed so that you can have your trial.
Unfortunately, a
whole bunch of the JRiver staff are away this weekend. I don't know if that trip will leak into the week or not.
I'll ask again, though... I've seen it happen with the Mac version "with my own eyes" (and 6233638 seemed to experience it as well). It does seem to be related to having later builds of MC19 installed, but I don't know for sure. Apparently, it is happening with the Windows version too, or at least to stenacho. To be clear, I did this:
1. Installed a clean install of OSX in a VM.
2. Updated it and whatnot and installed a few unrelated-to-MC apps.
3. Installed the current MC19 build (no previous install on the VM). Did NOT restore my MC19 license, just ran in Trial mode. Set it up by restoring a Library Backup.
4. Installed MC20.
Trial was expired on first launch.5. Trial of MC19 continued to work without issue.
If it would help, I'm happy to do additional testing in VMs (Windows or OSX) and provide whatever detail you require. Let me know.