nRF21540 UICR programming


I want to automatically load the value of POUTA_UICR into TX_GAIN at startup. The program code writes the setting value according to the steps on page 14 of the manual. It has been confirmed that the UICR Program state has been entered, and the VDD voltage value is 3.5V, but the values read by CONFREG2 and CONFREG3 are both 0. Can someone help me?

Best regards,