Permission denied when auth SMB with domain user

[Kosta]

Hello,
I am on the version 22.12.3.2 of TrueNAS Scale. I have two NAS at home, Synology Diskstation and virtualized TrueNAS.
What I basically need is an SMB share with same permissions on both NAS devices. Same owner, same permissions on AD groups etc.
When I try to mount the SMB share from another Ubuntu server with a specific windows AD user, I can only do that successfully with Synology. TrueNAS denies with permission denied. Both Synology and TrueNAS are of course domain-joined. Also, mounting the share with a local user on the TrueNAS does work.
What am I missing please?

Thank you

 

[Kosta]

And I found my issue, I had to use capitals for domain, for some reason Synology doesn't care, and Truenas does. Basically the same format as in the UI.