Looks like I found the issue. Had another tire shop dismount one tire and check the TPMS, its part #84961888. The shop ran the number and both that one and my 2021 part number are listed as correct for the 2019 Silverado. Seems with the body style change in 2019, (1500's got new body while 2500's and 3500's kept old body), both numbers were used interchangably. But the 84961888 will not work with 2020 and up even though both are 433mhz and both work in the 2019. The Tirerama shop has ordered me the new sensors and will be here Wednesday. Another couple hundred bucks gone.