Some HC05 modules have 2 AT modes. If you hold the button and power it up then release the button it goes into a "mini" AT mode. If you press the button, power the module and keep the button depressed, it will enter "full" AT mode. I use a small alligator clip to hold the button. Or you may, with some modules, use the EN pin or solder a wire to a pin to use to put the HC05 into AT mode. Do be aware that even though the module is powered by 5V the pins are not 5V tolerant.