Additional settings-related features and issues within Microsoft Teams for business
Dear Sergio,
Thank you for your reply. Since you’re in UTC+1, from the second screenshot (you’re 9h ahead), it seems that the shared mailbox is in UTC -8, but it’s in the same time zone as you. I recommend you check other contacts in Teams to confirm if this symptom happens to other contacts and test it in Teams Web App.
If issue continues in Teams Web App, I recommend you submit a service request in Microsoft 365 Admin center for I think it need to be checked on back-end. Please understand that we don’t have permissions to help check further. You can reach our online channel via creating a service ticket, our online channel will further help you address your concern: Get support for Microsoft 365 for business -- Online support.
Sincerely,
Etta | Microsoft Community Moderator