Don’t use “Save RD File” if you ever intend to “Open” it in LightBurn again. Use “Save” from the main file menu. “Save RD” is the equivalent of “Save UDisk File” in RDWorks, and is intended to create a cut file for running directly on the machine from a USB thumb drive.
If you’re at your laser computer, you could use “Run RD File” to send the “baked” version of the file to the laser, or you could load an LBRN file (LightBurn project file) that you saved from the other machine, and hit “Start”. The latter would be more flexible.