iPad won't accept Verizon SIM
Why not work through this checklist from Apple before contacting either the Carrier support or Apple Support?


https://support.apple.com/en-us/HT201415


Since you have a specific error message, you might also jump to one of the last steps first. Back up the iPad and restore it to factory new settings and re-test the SIM card that you think should be active.


https://support.apple.com/kb/HT201252


I've needed to call Verizon to get a SIM card to be part of a shared pool of data, but any active Verizon SIM should work, so once you rule out the iOS software - re-verify that the SIM you have is truly active.