Laser power level appears weak on any setting

I’ll do a power scale test (I have the 20 watt laser), and find my settings on a given material, then try to burn the material I tested on with the same speed and settings that the test shows optimal, and nothing burns. I power scale tested on a sheet of scratch art paper at 3000 mm speed and found that 20% power was my optimal power setting. So I then loaded an image that I have changed to negative using the “da big gimpin plugin” in Gimp. I set my settings as the tests said they should be and nothing etches. Had the exact same problem when I did ceramic tile as well. Great results on the power scale test, but on the actual image I get nothing like the laser is suddenly weak. I even set the power to 100% and it still looked weak with no results. I can hit the “fire” button and move it with the manual controls and it will etch fine at 20%. Try with the actual tested settings again, and nothing. Any suggestions?

Follow up. I had set my measurements to inches to frame easier. Once I changed it back to millimeters, it worked fine. Did this twice. Any reason this would cause that???