Error: Invalid DNS Server - Cellular Data

Hi— I use FortiClient with cellular data both directly on a Verizon iPhone and through ‘hotspot’ (on the phone) to connect an iPad and Windows laptop. As of about 2 weeks ago, I began receiving an Error: Invalid DNS Server message each time I try to connect any device through the cellular network. Any WiFi network works without issue and connection is no problem, however the cellular network can not connect. I used a colleagues Verizon phone with FortiClient and entered my credentials— no issue. I’ve contacted Verizon who says there’s nothing wrong with my line and to contact Apple or Fortinet for support. Uninstalling and reinstalling the app has not yielded any result. Anyone else experiencing? Any ideas or suggestions on how to resolve? Thanks!!