The reason for the error message should be visible in the error log. You can find it in your hosting area. If necessary, the support of your hosting can help you.
Alternatively, you could also enable debugging in WordPress. How to do this is described here: https://wordpress.org/support/article/debugging-in-wordpress/ – also here the support of your hosting can help you if necessary to edit the file accordingly.
In both cases you should be able to see what the cause is in the logfile. Often it is a plugin. You can delete the directory of the guilty plugin via FTP. After that you should be able to access it again.
If you still need access to the backend, you can reset your password in one of the many ways described here – even without this recovery link: https://wordpress.org/support/article/resetting-your-password/
I don’t need to reset my password to access the backend’. I just reset my password 2 weeks ago.
We have no support of our hosting so what I am supposed to do?
Even if you don’t have support from your hosting, you still need to have access to your files there. Then you should also be able to check the log file. And if that doesn’t help, as described in the link, you should be able to put WordPress into debug mode.
What irritates me now also: why do you need the recovery link to log in? I thought you can not get into the WP backend?
