I was curious to see if this should/would work, so I just now tested it.
My hardware is different, so I am really only testing whether an OBiTALK product can make and receive calls when its OBiWiFi5G is connected to a VZW hotspot via my VZW Android phone's hotspot feature.
It works great, in fact, amazingly well - as clear and reliable as using the OBi with my FiOS fiber optic Internet service.
So, you've got some other problem. If you have a MiFi device, why not try connecting directly to that device, without the TP-Link thing, nor any other stuff in the path - just VZW 4G LTE<-->[MiFi input<-->MiFi WiFi access point]<-->OBiWiFi5G.
If that doesn't work, I would not waste any more time trying to troubleshoot what sounds like your first foray into OBi-land. Instead, take the OBi 200 and a telephone somewhere else, that does have DSL/cable/fiber Internet service and see if it works. This will rule out some other problem first, and then you can focus on your MiFi problem.