Database Error after activating WooComerce

I have a big WordPress, lot of plugins in it,we´ve installed WooComerce also, but after activating it for a few minutes I start to get Error Database Connection, Does anyone know any Elephant in the room that I may be missing? Not an expert neither in WordPress nor WooComerce. Is there any known incompatibilities that causes this error? just to point me out a posible direction? Thanks!

 

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