ok, if your machine connects and home, no need to reflash anything, it means GRBL is still alive and kicking.
The thing is, Lightburn uses slightly different GRBL parameter values than Carbide Motion, and this is probably what causes your problem.
To reset the GRBL parameters to their default values (for CNC/Carbide Motion use), you can just go in the Settings menu in CM, reselect your machine type & options, and click ‘send configuration’ (or something like that, I don’t have CM open right now). This should resend all GRBL params.
Hopefully that will restore your machine back to working condition, but then of course it won’t be correctly configured for using Lightburn anymore. What I do is, I have a set of macros in Lightburn to switch back and forth between CNC mode and Laser mode. See this post for example. It’s all taken from this video.