If you've tried everything reasonable (uninstall/re-install Android Pay,add/remove cards/etc.),I'm stumped.
Only things that come to mind are the cards aren't compatible,or,wherever you've tried to use it doesn't accept it.
If that's not the case,seems to me a factory reset is the only other possibility of getting it to work.
However,since Google has acknowledged that they're "working on it",I doubt there's much you can do short of a reset,or,find someone with a Verizon LG V10 who has had success in using it.
If they get it to work,perhaps there's a hardware issue w/your phone.............