Help getting MKR to work with Freedompop

I'm trying out a Freedompop SIM in the US. I'm starting with the SendSMS example. Here my log...

SMS Messages Sender
⸮AT

OK
AT+IPR=921600

OK
AT

OK
AT+UPSV=3

OK
AT+CPIN?

ERROR
AT+CPIN?

ERROR
AT+CPIN?

ERROR
AT+CPIN?

+CPIN: READY

OK
AT+CMGF=1

OK
AT+UDCONF=1,1

OK
AT+CTZU=1

OK
AT+UDTMFD=1,2

OK
AT+CREG?

+CREG: 0,0

OK
AT+CREG?

+CREG: 0,0

...

OK
AT+CREG?

+CREG: 0,1

OK
AT+UCALLSTAT=1

OK
GSM initialized
Enter a mobile number: +1xxxxxxx
Now, enter SMS content: SENDING

Message:
Testing.
AT+CMGS="+1xxxxxxx"

> Testing.
+CMGS: 5

OK

COMPLETE!

But nothing gets sent. Can someone help me debug this?

Do you need to use the country code pre-fix when you send a message to a mobile number? I didn't think you would. I guess you've tried a few different numbers and possibly tried a different SIM card with the same sketch just to make sure it's not a problem with that one?

What else have you tried to troubleshoot the issue?

Looks like you connect to the Network okay and then it obviously gets sent to the network, do you have credit on the SIM card and everything?

Are sure that FreedomPop have sms service? as far as I know FreedomPop is providing data service only, and if you want to use sms service on your phone then you need to install their app (because it sends sms from the internet)