Raspberry Pi/DVAP connection problem

Did you configure the gateway by running DStarConfig.exe after flashing the image? No changes to the python program are needed--all of the configuration data necessary to set up the gateway is written out when you run the config program.

I doubt that using the DR mode programming in the ID-51 is going to work with the gateway. You need to set up your radio to send the appropriate linking commands on the freq you have configured for the gateway and in DV simplex mode. e.g. to connect to reflector 12 module A you have to set up the radio to send the linking command by placing "REF012AL" in the URCALL field. Most folks program their radios by setting up memory channels with the linking commands for their most often used connections.

Regards