Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Dear 이민지1,
Good day! Thank you for posting to Microsoft Community. We are happy to help you.
As per your description, it seems that you are having issue accessing Loop either from the app or in browser.
If the understanding above is right, please check if changing to another network or sign in in another device such as your mobile can reproduce a similar situation, please also check if you can access M365 portal as expected.
If issue persists in different browser with different network on different devices, please check if resetting your account password can help. If not, we're afraid this issue may need to check from backend service for further investigation. As forum support, we may not have enough permission and resource to directly check the environment on your side, more resources need to be involved in to help you further.
We notice you post this question in For business category, so we suppose you have Microsoft 365 for business subscription. In this situation, we sincerely recommend you contact your Microsoft 365 administrator, follow steps in this article and try to create a support ticket to contact Online Support. The support team over there has higher permission than us, they can remotely help check the situation on your side, involve more resource to collect logs and help you do troubleshooting. This would be a more efficient way in handling this case for you.
For reference: How do I find my Microsoft 365 admin?
If the understanding above is not consistent with yours, please feel free to post back and point that.
Sorry for the inconvenience again. Your patience and understanding are highly appreciated. Hope you stay safe and healthy.
Sincerely,
Rhoda | Microsoft Community Moderator