Weird. This whole system is a real pain in the ass. I put the three wheels that I can't get a response from in my spare bedroom last night. I was thinking that moving from 40-ish degrees to 70-ish degrees may help the batteries enough to get them working. No luck.
Since I have to break them down anyway, I am going to try deflating them and see if maybe they will trigger that way.
The VT30 does tell me what the battery condition is in each sensor. Battery life is reported as 'OK' on all the functioning sensors, but I am not sure where that ranks on the battery life scale.