An error occurred while fetching the board lists. Please reload the page

Hello, I am a bit new in the Gitlab world and I am facing a problem for which I did not find a solution.
In “Issues”, when I want to access the boards, I get the following error: “An error occurred while fetching the board lists. Please reload the page.

Does anyone have an idea how to solve this problem?
Thank you in advance.

Best regards
Eric