License key error

My license key says it doesnt work for rhino for mac, what should i do?

Please provide more detail so we understand the problem.

Are you by chance trying to use a V6 license key (RH60-xxxx…) in V5 for Mac?
If so, that will not work.
If you requested the V6 eval, then the first item in the message is a link to download V6 for Mac.
Download it and replace the old Mac V5 with V6.