Front Unit not Reading Back Transducer

My front 106sv is wired to a small lithium battery and console 106sv wired to crank battery. Dealer had to replace the lithium battery and front unit will no longer read back transducer - which is shared between the two units. Anything obvious to look for?

Both unit must be on. Make sure same updates on both.

Check your transducer source on the unit not working.