There are two methods for using AT mode. One involves a blank sketch and a pass through method with Rx>Rx and Tx>Tx.
https://howtomechatronics.com/tutorials/arduino/how-to-configure-pair-two-hc-05-bluetooth-module-master-slave-commands/
The other involves using a software serial connection with Rx>Tx and Tx>Rx.
https://forum.arduino.cc/t/setting-hc05-zs-040-to-at-mode/1059616
Which method are you trying to use?