I am also having the same problem on two hc05 boards I got from DSD Tech https://www.amazon.com/HC-05-Bluetooth-Pass-through-Wireless-Communication/dp/B01G9KSAF6/ref=pd_sim_147_1?_encoding=UTF8&pd_rd_i=B01G9KSAF6&pd_rd_r=50VWASGP2VZFFHFXYYA6&pd_rd_w=UdL2T&pd_rd_wg=nBVeR&psc=1&refRID=50VWASGP2VZFFHFXYYA6
I am using SoftwareSerial to try to communicate with the module.
I have also used a restart method that directly connects to Rx and Tx using delays before sending the AT commands.
I can not get a response from the board in AT mode.
Felic, if you could post where you got the board we can see if it is a manufacturer error or something.