I just found this this reply in another thread:
"How many Portals do all of you use? This may be an issue with storage of sign-in credentials, added in 3.0; every sign in credential gets added to the Windows Credential Manager, and if it ends up storing too many of these credentials, the sign in can fail to open.
If this is the case, then it can be solved by deleting all of the Survey123Connect entries within Windows Credential Manager, which can be accessed through the Control Panel."
Removing the 2 Survey123 Connect entries from the Windows Credential Manager solved the problem.
Thanks,
--gary