Forum Rules:
Before creating a support thread here then please read [Read Before Posting] Ask For Technical Support: The Right Way.

No combat log in Chat frame - how do I activate it?

I am sorry - I misunderstood you there.

I have found out what caused the problem meanwhile. It was not ElvUI. It was another Addon -> Leatrix Plus which has a feature to turn off combat log... for whatever reason - and it was flagged true. So everything is fine now - thank you for you help!