Problem:
I've been creating some general list / libraries in SP Online Enterprise and customizing / creating a few forms. I've been querying different lists for data and such as well.
Monday was a normal day doing these tasks. Tuesday I start getting sign-in requests and it fails.
Sign-in Prompt / Result:

Items verified:
- Credentials are accurate.
- All other office products product no sign-in errors.
- Rebooted
- Waited overnight - hoping for some general glitch to work itself out.
- I have Site Collection privileges on connecting site
- Attempted on other sites where I am a general admin with same result
- I use Win10 and always have without issue.
- Feature is active
- I've checked with our IT administrator and he indicated he is not aware of any changes that were done recently.
Issue presents itself with any InfoPath connection to SP.
- From Designer trying to query data
- From Designer trying to preview; querying data
- From Designer trying to publish
- From SharePoint trying to customize in InfoPath button (shown above)
Any thoughts or advise is appreciated.