Forgotten Passcode and Data Transfer to iPhone 12 Max Pro

I recently purchased a new iPhone 12 Max Pro, turning in my iPhone 11 Max Pro in trade. The T-Mobile rep setup my phone to transfer the data from one to the other. When it asked for the passcode for my old phone, i couldn't remember it so he bypassed it. After setup of the new phone was complete, the old phone was wiped. I have since realized that my contacts didn't come over correctly. When I attempt to reload it, it says my iCloud account is corrupt. When I try to fix that, it asks for the passcode to my old iPhone (which I can't recall but the phone is wiped anyway). The next message said that I can reset the encrypted data. What do I lose with that act? Is that going to help anyway because the version 11 phone is clean.