Hi
I am not an O365 Admin. I have SUPER and SECURITY roles in BC and those roles do not have a company assigned to them as I can work across all companies. I can use the Get Users function without error - so Olena - definitely try adding the SECURITY role.
Also, just a note because this happened last week. My O365 administrator added some new users for me, he logged into their accounts to ensure they were activated. They would not appear in BC when I used the Get Users. I stumbled across another post somewhere that said the user needed to log in for them to appear.
So I logged in as each user and switched into BC with that user - then they appeared in the users list and I could assign all the security after that. Just something to keep in mind if you get past the error message - but they still don't appear.
Cheers
Heather