Seeking Code & UX Feedback on my PHP License Manager

I built this PHP license manager, but it wasn’t accepted on a marketplace. I’m looking for honest, critical feedback to help me improve for my next project. I’m particularly concerned about security, code structure, and usability.
I can also provide a link to a public GitHub repository with the code.

Demo login details would be better if it’s provided.

Thank you for your submission. We have completed our review of “ConversioKit” and unfortunately we found it isn’t at the quality standard required to move forward, and you won’t be able to re-submit this item again.