I got this error message after changing the target board from a NANO with old bootloader to a MEGA 2560. Restarting and reopening XOD doesn’t work.
After saving the project (with the new upload settings) and uploding again it worked correctly.
Begin compiling code for the board Arduino/Genuino Mega or Mega 2560
Error: Error resolving FQBN: getting build properties for board arduino:avr:mega: invalid value ‘atmega328old’ for option ‘cpu’
C:\Program Files\XOD IDE\resources\arduino-cli.exe --config-file=C:\Users\OPTIPL~1\AppData\Local\Temp\arduino-cli1ts1fB\.cli-config.yml compile --fqbn arduino:avr:mega:cpu=atmega328old C:\Users\OPTIPL~1\AppData\Local\Temp\xod_temp_sketchbook2nDXN0\xod_1540576586285_sketch failed with code 1
The generated C++ code contains errors. It can be due to a bad node implementation or if your board is not compatible with XOD runtime code. The original compiler error message is above. Fix C++ errors to continue. If you believe it is a bug, report the problem to XOD developers.