MK2i Suddenly can't communicate with T1 underwater

I have used the MK2i with the T1 (2 of them actually, mine and my wife's) withg my MK2i for 12 previous dives where everything worked flawlessly.  

No previous problems pairing or connecting. 

Today, on two dives, my MK2i simply would not connect underwater.  I could read pressure while on the surface.  As soon as I submerged, and the unit moved to sonar, I lost connection with both T1 transmitters.  Nothing.  No air pressure data at all.   Batteries on both T1 transmitters read as new.  

The only thing that has changed since the last time I successfully used it was that after my previous dive, I tried to update the T1 firmware.

The MK2i connected briefly with the transmitter, but failed to update the firmware on the transmitter.  

I'm wondering if trying unsuccessfully to update the T1 firmware has somehow made my MK2i sonar non-functional.  

Anyone with any recommendations about how to fix this issue?