@javajoeuk said in tool board connection problem:
Warning: Board 121 does not have input handle 3000
That warning is produced when a M574 or M950 J command is run (normally from config.g) and the main board thinks that the endstop or input being defined currently exists on a CAN-connected expansion board (so it tries to delete it); but it doesn't exist there. For example, if you reset the expansion board using M999 B# (where # is the CAN address) or you upgrade the firmware on an expansion board, and then you run config.g without resetting the main board, you will see that warning.