The issues was picking the correct band. After looking through the MKRWAN code I found a second US band option: US915_HYBRID. After switching to that, all is well.
modem.begin(US915_HYBRID)
The issues was picking the correct band. After looking through the MKRWAN code I found a second US band option: US915_HYBRID. After switching to that, all is well.
modem.begin(US915_HYBRID)