activating iPhone 11 Pro Max on Sprint

I bought an iPhone 11 Pro Max and used it with Verizon for the past few months. Now I want to switch to Sprint, but Sprint won't add this IMEI to their database and allow me to activate it. Sprint says "Device has incompatible Apple activation policy. Device is not compatible with the Sprint network (international device) and will not be added to Sprint inventory."

What can I do to get this fixed? What is this activation policy that Apple has?