The first thing I do when having troubles with something in Qubes I search qubes-issues. In your case I’d search for “qrexec-daemon startup failed”. Don’t forget to look at the closed issues as well.
If you don’t find a similar issue (and a possible solution) I’d try with a fresh template via sudo qubes-dom0-update qubes-template-fedora-33
Also, I’d think about keeping a virgin template and cloning it before installing any software in it. This way you can always go back to the fresh template and clone it again when something breaks or doesn’t work anymore or just for testing purposes.
Like @icequbes1 said before, I also experienced trouble with different qubes when running out of space in the dom0. In the Disk Space Monitor you should find varlibqubes and dom0 (don’t know the exact term). If you hadn’t changed the default setting it should be 20GB and not 200GB. Are you sure you have 200GB in dom0 left?