You might need to install other software to open this address."

Every time I try to go to a custom protocol URL to get redirected to a program for things like website sign-in I get this error page instead of it working or offering the program selector. "The address wasn’t understood Firefox doesn’t know how to open this address, because one of the following protocols (cag) isn’t associated with any program or is not allowed in this context. You might need to install other software to open this address." The protocol shows up in the applications setting and is pointed to the correct program. I have made sure my Firefox and Windows 10 are fully up to date. I tried launching Firefox in safe mode. I actually completely reinstalled my computer. It works briefly until a little after sync completes but the computer it is syncing from does not have this issue. This issue has occurred so far with Slack and Datto RMM. Any help would be fantastic!