HI @jutta.biesemann, thanks for reaching out!
If you originally created and owned the board, it's possible that you're now accessing it through a different Miro account registered under another email address. Another possibility is that your access to the team where the board is located has changed, which may explain why you now have viewer permissions.
To help narrow this down, could you please double-check that you're logged in using the same email address and Miro account you used when you originally created the board Edition? Also, you mentioned that you may have done something that led to this change. Could you share what actions you took before you noticed that you had lost your editing rights? For example, did you change accounts, email addresses, team membership, or any board settings?
This additional context will help us better understand what might have caused the issue.