Error RPC 500 when trying to connect to Zebra ZD621-203dpi via serial port


I’m having an issue while trying to connect a Zebra printer (ZD621-203dpi) via serial port, the player return an error “Internal Server error [500]” when I call the “Run Device Function” as follow :


The error message is “Failed to call RPC “Connect” on “Serial (Player Only)” : Internal server error [500] [RPCError]”.

Have you already had this kind of issue?

Thanks a lot and best regards,


Hey Antoine,
Thanks for reaching out. As you are using the serial driver, make sure to be connected to the RS232 port on the back of the printer, and not to the USB port.
Also, in order to find out what path you should configure, you can use the “List Ports” function of the Serial Driver to list available ports.
This Knowledge Base article walks through the process! Using the Serial Driver


Hi Antoine,
I had a similar error with a Zebra at a EdgeMC device. And after a long research I fount out, that a variable, I sent to the template, was empty.
But because you are using static values, check of following spaces or misspellings.
Check also the connectivity with the
Zebra Connectivity Setup Wizard
What do the
Run Device Function → Serial (Player Only) ->List Ports


Hi Hugo and Chris,
Thank you for your answers, I will test tomorrow with a new cable that we juste received to connect the printer in RS232 (it was indeed connected via the USB port).
I will keep you up to date.
Best regards,

Hello both,

As soon as I connected the Zebra printer using the RS232 cable it worked perfectly.
Thank you and best regards,