General Introduction
If you just enabled Azure AD Identity Protection for your entire tenant, you might get some complaints from guest users, saying that their sign-in was blocked.
If you got a similar issue, but the user is not a guest but a member of your organization, follow this guide:
https://azvise.com/2022/05/25/unblock-at-risk-user-azure-ad/

You cannot remediate the user risk of a guest. If you try to look for a guest user in Identity Protection | Risky users, you won’t find any.
The user risk is calculated in the “home” tenant, where your user was created, not in the tenant you have guest access / are trying to access. This is also done so that the system may have more insights into user behaviour to calculate the risk.
How to resolve
Now going forward, there are two ways of solving this issue:
- If the home tenant administrators have AAD Premium P2, they can remediate the user risk by following this link Identity Protection | Risky users. A password reset is usually suggested and will also clear the user’s risk.
- If they do not have AAD Premium P2, they can reset the user’s password or let the user do it by themselves by using Self Service Password Reset (SSPR), if configured. Alternatively, they can also go on this page, and ignore the user risk, once you have assessed that everything is resolved: AAD Risky Users. All these methods will clear the user risk.
Of course, if you wish, you may disable the user risk policy for guests. This is done by creating a dynamic group in Azure AD containing all the guest (Dynamic security group with a dynamic query of usertype equals guest) and excluding it from the policy.