I had the same problem and opened this topic. According to Ryan, all you have to do to fix the problem is add the following g-code command to your start g-code:
M3 I
If you are new to Lightburn, start g-code can be added in the GCode tab of the Device settings dialog.
I had rolled back to a previous version of the firmware (that did not need this code), and have yet to upgrade again and test his fix. Apparently, this new g-code command is necessary due to some significant changes in the laser code with the latest version of the firmware.
Or, if you cannot get your laser working with this code, and you need your laser working, you can roll back Marlin a version or two.