AI A6 Ceullar module. Problem with UART?

[mrpackethead]

I coud'tn help myself but to buy a couple of AI A6 Cellular modules the other day when i was buying some 'real' parts from a supplier..  Given they are so cheap.    I have installed a valid Sim into it.

 I plugged it in last night,  on a 3.3V TTL serial adaptor..  Serial port is set for 115200, 8bits, No parity, 1 stop bit.   
I've had a couple of lines of text come back  saying "CINIT 2, 32, 41891"  etc etc   But not relaibly, it doe'snt do it all the time, just sometimes

I try to send a AT command, but nothign returns.. Its almost like the device is not getting my commands.

I've checked my Serial interface, by plugging in a loopback and it seems to be working ok.

Does anyone know if the TTL interface shojudl be 3.3V or 5V?   I've got two of them, and they are both doing the same thing.    I dont' have a 5V TTL interface,  so not sure if i need one.

EDIT.  i tested the Serail interface on a beaglebone black just for good measure.   It works without any issues.  So either i have some kidn of level incompatblity, or theres some other issue.