@Victoria Ivannikova - Google Translate may be failing me here, but it sounds like you lost access to a Miro board. When this suddenly happens, then the owner of the board likely changed the permissions or, if you were the owner, then an admin of the team space where you the board existed likely removed you from the team.

Here is a post I put together with a few possible resolutions.

https://community.miro.com/ask-the-community-45/article-how-to-find-and-hopefully-recover-a-lost-or-missing-board-13123