Yeah, I got that 403 error a couple of times this morning too. I clicked the back button and tried again and it finally accepted my post. First time I've seen that.
S50 is too much power for focusing. Try S10 or S15.
What software are you using?
Did you write your gcode test file?
Have you tried using the gcode file I posted on
Benbox Laser DIY Machines - Index ? That one makes all the passes in one gcode file so you don't have to restart your 'program' for each pass.
And please tell me again what machine is this?