Hi @Matthew Beck - thanks for your question.
It's possible that your users are hitting one of the scenarios covered by https://learn.microsoft.com/en-us/outlook/troubleshoot/authentication/outlook-prompt-password-modern-authentication-enabled (basically, related to having migrated from an on-prem Exchange to M365).
Can you take a look at that and see if that helps?
If this helps, please remember to upvote and mark as answer so that others can find the solution in future.
Well I need to get in there to determine which it is for those two users.
But when I look under settings, I see no option for Modern authentication , as shown below.
Is there a different settings I should be aware of ?
Apologies @Matthew Beck , I missed that it's under "Org Settings" in the settings drop down:
If it's only affecting a few of your users, though, then it sounds as though it's more likely that modern auth is enabled (it is enabled by default and it would impact everyone), but the affected users may need the registry updated.