Problem Sharing Power BI Report to One External Client - We are on Fabric Capacity Plan F64

Thanks to everyone for their helpful replies.

The client eventually came back to use to let us know the error message they were getting.

"Your account is blocked. - We've detected suspicious activity on your account.  Sorry the organization you are trying to access restricts at-risk users.  Please contact your <client's orgiansation name> admin."

Not sure from this as to whether it is their org or our org that is doing the blocking.  We've asked the client to check the following:

• Recent Activity: https://mysignins.microsoft.com
  • see if their login is getting blocked and any info we can get off this
• Organisations page https://myaccount.microsoft.com/organizations 
  • This should show our organisation as a collaboration organisation
• Risky Users report: https://portal.azure.com/#blade/Microsoft_AAD_IAM/SecurityMenuBlade/RiskyUsers
  • Hopefully we will see the users in this report and be able to clear them for access

We are also doing the same within our organisation.  Hopefully this will point to where the client's users are getting blocked.

As a general comment Microsoft documentation that people have pointed us to - it's partially out of date.

With the introduction of Fabric and the F64 SKU capacity plan, you don't have to go down the full B2B sharing route.  All you have to do is the ad-hoc sharing route as described in https://learn.microsoft.com/en-us/power-bi/enterprise/service-admin-azure-ad-b2b

Essentially, you are treating externals like they are an internal user and Fabric takes care of the rest.

Thanks again to veryone who replied.  I'll update the post once we find out where the blocking was coming from.