What?

That’s a direct translation; better English equivalents would be “give it a try” vs. “look forward to it”. They are pronounced similarly (tameshimi/tanoshimi) and either makes sense in context (usually heard at the end of an ad), so “Please look forward to/get excited about X” and “please give X a try” both would make sense.

Commercials are saying お試しみしてください and not お楽しみしてください.

No， it was not natural.