ok weird one i wrote a simple unit file for our app... running teh command manually works perfectly. runnnig it as backup.service:

This app can't run on your PC
To find a version for your PC, check with the
software publisher.
systemctl status shows sattus=200/CHDIR and thats it. No useful message. Ive reloaded the daemon a dozen times.
ive compared the command in ExecStart with what i type in my shell character by character. they look identical. the service user exists. im clearly missing somehting about how systemd runs things, but i cant figure out what it is.