Hi @MMRot ,
Thank you for posting in this community.
Is the popup login window like the one shown below?
Here are the possible reasons and what can be tried:
- Browser cache can interfere with SharePoint functionality. Go to the Chrome browser settings>Privacy and security>Site settings>scroll down to Content>Pop-ups and redirects>check whether pop-up is allowed.
If yes, block it, clear the browser cache and then relaunch the browser to do a test to see the result. Did you try to access the link thought a different browser.
2.Sometimes, the pop-up window is related to network connections. Try the following:
- Navigate to Control Panel > Network and Internet > Network Connections.
- Right-click on the Ethernet connection and turn off the authentication option.
3.Someone put in a ticket to MS support, Conclusions reached:
- If you have no O365 profile info saved in your browser (or you're in private browsing), you are not prompted to log in anymore.
- If you do have O365 profile info saved in your browser, you are prompted to log in with your O365 account. However, now it doesn't throw an error if you log in with an account that is not part of the organization that owns the shared resource. Once you've logged in, it does not ask you to log in again.
Hope the information can help you. And if there have any unclear or misunderstanding, please feel free to post back and we’ll continue to help you all the time!
Your understanding and patience will be highly appreciated! Hope you have a good day and keep safe!
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.