Login fails : Sorry, something is wrong with your data
recently its not possible to log in my forum.
After entering the login data, a white page appears with the text: Sorry, something is wrong with your data I tried to delete the cache. it doesn't work.
Do you have an idea what it could be?
Delete All your website Caches, then navigate to Dashboard > wpForo > Overview Admin page and press Hard Flush Permalinks button.
And also check this FAQ Topic about Cache: https://wpforo.com/community/faq/wpforo-and-cache-plugins/