Microsoft project management software used to plan, manage, and communicate a project schedule and other information among workgroup members, project managers, and other stakeholders.
Dear Miłosz Pytel,
Good day! I hope you are doing well.
Unfortunately, my team and I are unable to assist much with this type of error as it might require running some backend diagnostics. I sincerely apologize for any inconvenience this may cause.
I recommend you try to contact Microsoft directly by any of the methods provided in the following link: Get support - Microsoft 365 admin | Microsoft Learn. They should be able to offer the specialized support needed for this issue. This is a long shot; however, in the meantime, you could try to unassign and reassign your project license.
I really wish I could be of more help. Please let me know if there is anything else I can assist you with.
I appreciate your patience and understanding and thank you for your time and cooperation.
Sincerely,
Ralph Chawatama | Microsoft Community Moderator