You can have your PEMPro License key emailed to you if you have forgotten it. The email address can be what is on your original license key, or if you have previously changed your email address, your new email address.
If you don't have access to that email address then you can create a support ticket at this link:Submit a support ticket
Note for Astro-Physics mount owners: if you have a PEMPro V2 or V3 license key that you received with your Astro-Physics mount (it looks like "XXXXX-XXXXX-XXXXX" or "XXXXX-XXXXX-XXXXX-XXXXX-XXXXX"), and you haven't previously requested and received a 13-line PEMPro V3 license key, then please see here. If you previously requested and received a 13-line PEMPro V3 license key for your Astro-Physics mount, but lost it, then you can use your email address to retrieve it below.
Once you get your license key, if you ever need to change your email address, see the Other Options section below.