A donate is an appriciation to the developer/s but it's not the same as buying a software.
In case of MarketEnabler, a donate will get you a donate key that removes ads from the application and adds some beta functions that are still in testing.
Please look into your SPAM folder as it is an automated script that sends you the key.
If you don't get an answer after 24 hours, please email me at email@example.com.
Are you sure that you have a working su binary and busybox (or at least the killall command) installed and granted root rights to MarketEnabler when it got requested?