Laser isnt cutting throught on same wood

I’m having issues with my laser will stop cutting through the wood…i thought it was the wood itself which has been the case in the passed but cutting the same wood…i was running at 15 speed and 90 power now i have to go 5 and 95 and 3 to 4 passes on the same wood…ive cleaned everything double check focus and alignment and i still cant figure out what is going on…can someone help