!Help asap! - happy to pay

Check focus and if your laser lens are clean.

Both checked. Still not enough power to leave a mark!. Weird!

At what speed?

You need to systematically go through the GRBL settings and reconfigure them for your machine. There are several guides that can walk you through the process. Here’s a quick cheat-sheet I found that might be able to help:

Here is the full explanation:

And here the specific lightburn docs on the topic: