Thanks for the post. You can find information about AerFrame error codes here.
Regarding your specific issue, it's not uncommon for signaling messages to either not be received or become out of sync. These issues usually resolve themselves quite quickly, but in rare cases we have to clear the registration of the device from our network and from our Carrier partner network.
In this case, we cleared registration for your device, it re-registered, and we sent a test MT-SMS successfully.