@axk5216 If you are getting an "ERROR" message this means that Grbl has reported a problem and for safety T2Laser shuts the laser off. This error message is usually a result of a memory issue on the Nano, with the latest Chinese clones it has become more frequent and appears to be due to over heating of the Nano. The best fix is to get a genuine Atmel based Nano, these are a few dollars and much better performance than the Chinese knockoff.
Other causes are a bad USB cable or electrical noise on your machine.
You can enable Simple Streaming from the menu to eliminate most of these memory issues, but if your computer is not fast enough the laser could stutter during engraving which will ruin the result. You will need to test it. It's a way to diagnose the problem and should not be considered a fix, just a band aid until you replace the Nano with a better quality part.