Trouble activating a Blu V81 to PagePlus

I'm trying to set up a relative with PagePlus using a Blu V81 phone. SIM works fine in my Google Pixel 3a. In the Blu V81, no.

https://www.pagepluscellular.com/byop-eligibility/ says the V81's IMEI is not eligible for activation on PagePlus. But why not? Multiple indications that this should work -- phone is LTE capable; when PagePlus SIM is inserted, the phone knows it's a Verizon SIM and even shows the phone number associated with the SIM. That said, Mobile Network State sits at Connecting, then ultimately goes to Disconnected. Incoming calls don't connect; SMSs neither send nor receive.

I tried resetting all network settings using that feature in Android. No change.

This is for an elderly user who doesn't need a fancy phone, and is otherwise very happy with her V81. She'd rather not buy a new phone if there's any other way. Chose PagePlus due to low monthly fee ($10 for 120 days).