Multisite Subdirectory Site Dashboard redirect loop

I spoke to the web host, WP Engine, who advised us that an extra license is required to turn a WP site into MU, which we don’t currently have.

They confirmed the error was caused by our lack of a MU license.

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