Where do I find my registration number? MAMP GmbH August 27, 2014 11:16 Updated Follow Open the dialog File/About MAMP PRO, it is shown there. Related articles How do I recover my license key / serial number? I want to revert back to MAMP PRO 4.5. How do I unregister my MAMP PRO? I upgraded to MAMP PRO 5 and I am missing databases. I did not receive my invoice?