I upgraded to 10.30.3 yesterday and noticed now that my macOS Self Service is not connecting, iOS Self Service is still operational. There is no crash like I've read others experiencing. I am working with support on this, just curious if anyone else has ran into this and possibly found a fix?
I was running into this issue this morning. I was attempting to install some VPP apps from Self Service and it was failing immediately with the error reported by OP "Couldn't connect to the Jamf Pro Server. Try Connecting Again". I checked to make sure I could retrieve policies and ran recon all fine, so I uninstalled and reinstalled Self Service and seemed to clear up the problem. If the issue comes back I'll update.
I might have a new cause and fix for you. Support found my problem. If you currently have any macOS Configuration Profiles that have "Make Available in Self-Service" it is causing Self Service to have this problem.
Fix and I quote Austin from my support ticket "You can either set this to deploy automatically or disable/delete it. If this fixes Self Service, we are running into PI-009440, a known issue with this version of Jamf Pro that is caused by adding a malformed Configuration Profile to Self Service."
I hope this helps!