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

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.

The account is over 4 months old an I tried to add the Users three months ago, in one day. The Tenant with guest Users is from a government organization which I work for. The last few days I tried and tried again. But still the same error. I've tried the Guest Inviter role and the settings for guest users...Still the same error.

What am I doing wrong?

Please help.

Regards,

Jorrit Wagenaar