Error when inviting external users in MS Azure "User invitation Failed"

Question

Hello,

When i try to invite external users in MS Azure I get an error:

"User invitation Failed"

"Insufficient privileges to complete the operation"

I am a Global Administrator

I added the external organization in Cross-tenant access settings and I allowed all the settings for External collaboration.

I've already added 11 external Users, and when I tried to add the 12th, I got this error.

What am I doing wrong?

Please help.

Jorrit Wagenaar