I have an Omtech Turbo 756 with Ruida controller and Lightburn. All works fine except the frame area is not over the knife bed, it is too far forward so anything that is cut at the front edge of my plastic sheets gets some black burn/flashback from the metal frame. In the attached image (not my laser, purely made as an example!) the red line shows the laser frame area, you can see it is too far forwards.
If this is a typical OMTech (with some nice bells & whistles), then the Y axis home switch is in the right rear corner. It sets the rear-most boundary of the 700x500 mm “processing area”.
If that’s where the switch is, then you must move it further back to shift the “processing area”.
However, I expect your machine is similar to mine, with the Y axis switch mounted on the frame, firmly against the rear bulkhead, where it cannot be moved in any direction. The travel in my machine extends slightly forward of the knife blade area, too.
Basically, everything OMTech tells you about the laser is truthy: it’s correct, but not exactly what you expected.
The X and Y axes have a small pulloff distance from their limit switches, so while the overall “processing area” is 700×500 mm, you can only use the front / left 695×495 mm.
You can probably tinker a bit with the pulloff, but at the cost of having the home position become less reliable, so it’s likely not worthwhile.