tire pressures only displays 1, maybe 2 tires

[mkaye]

in the spring i got new tires and had all the TPMS sensors replaced (purchased from Lexus dealer in Texas from ebay)
loaded all new ID's & had tire pressure symbol as i left the shop (Costco)
my mechanic checked & 1 was reporting 3psi, not 30, had it replaced, mechanic loaded new ID
a few months later had a rim leak, checked the tires and found the low 1 on the 3rd tire, added air, had tire repaired
a couple of days later, only 1 tire pressure is on the display, not yellow tire symbol, just 3 empty slots
had my mechanic check today, all sensors have good battery & appear OK
he reloaded all ID's, on the way home i had 2 tires reporting, which sometimes happened
what can i do to reset the system in the car?
 

[mkaye]

put my winter tires on, loaded ID's - all registered

i can only assume all the ones i bought on ebay have weak transmitters