The laser did not reach the set power

If you notice that your laser engraves at a lower power than the S-Max setting in LaserGRBL, don't be alarmed—it's expected behavior when M4 (Dynamic laser power) mode is turned on. In this mode, the software commands the requested power level, but the controller dynamically adapts it to account for direction changes, acceleration, and maximum speed constraints, all while factoring in the grayscale value of each pixel.

S-Max was set in LaserGRBL but the actual power was low, usually not due to software failure, but rather a mismatch between the settings of LaserGRBL and the machine controller (GRBL firmware). Simply put, software and firmware have different understandings of the value of 100% power.