My New laser (ORTUR 15W) became very weak after 20~30 times test

My New laser (ORTUR 15W) became very weak after 20~30 times test.
At the beginning, I did not have the problem and it cut the thin wood very well
and engrave the leather very well.

But, today, after a few times engravement job on the wood, the laser power became very weak
and it can not cut even one pcs paper !!!
Fan is running well. But, power is very very low even at 100% power.

No connection problem and no setting problem. It just does not provide the strong power suddenly.

What can I try… OMG…

I bought this laser from the following link.

Anyone who has the similar experience?