It can be tricky getting the Mac into DFU Mode. I've done it a lot of times, but I still have trouble sometimes. Sometimes it may take me a few attempts.
If you leave the Apple Configurator app open, then you can see the status of the Mac you are trying to put into DFU mode (sort of anyway). You don't want any status in the Apple Configurator window which indicates the laptop is powered off. This way when you press the keys & hold them you are more likely to enter DFU Mode.
Here are the Apple articles with instructions for using Apple Configurator and putting the Mac into DFU Mode...one for Intel Macs & one for Apple Silicon Macs (M1, M2, M3). While these articles may mention not to launch Apple Configurator early, I always make sure Apple Configurator is running on the host Mac before I attempt to place the "broken" Mac into DFU Mode.
Revive or restore an Intel-based Mac using Apple Configurator - Apple Support
Revive or restore a Mac with Apple silicon using Apple Configurator - Apple Support
Another very important part is making sure you are using an Apple USB-C charging cable and it is connected to the proper port on the "broken" Mac. For some unknown reason, the USB-C port required is different between the Intel & Apple Silicon Macs which makes things even more confusing. The USB-C cable must support both power & USB data. The USB-C cable must NOT support the Thunderbolt protocol....usually the USB-C connector will have a lightning bolt symbol on it if the cable supports the Thunderbolt protocol. It really is best to use the original Apple USB-C charging cable which shipped with an Intel laptop....if you have an Apple Silicon Mac which shipped with a MagSafe cable, then you will need to purchase an Apple USB-C charging cable.
And make note of which keys you press are on the Left side or Right side of the keyboard.
