Upload file type not permitted even if explicitly registered as upload_filetypes in the db (multisite)

Known issue that was introduced in 4.7.1:

https://core.trac.wordpress.org/ticket/39550

There is a plugin to workaround it for those having this problem. A fix will likely be in the next release.

https://wordpress.org/plugins/disable-real-mime-check/

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