WordPress comments just vanished even tho there are about 250+ of them. Where did they go?

first thing I would do is to deactivate the Cache and see if that makes a difference. If disabling solves the problem, reset the cache for the comments of the particular post.

Probably something went wrong for the caching strategy and it ended up in some useless state.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)