My Ortur Laser Master 2 always worked fine with my MacBook Pro running Mojave. Just updated to Big Sur and Lightburn 1.2 (Big Sur) and now I cannot run my laser. When I “Add Device”, it finds my laser. However, when I try to run the laser, I get "Port failed to open - Already open?
I had similiar issues on my mbp 15 running 12.4 (IIRC), save your work, shutdown lightburn and start again. Seems to resolve it.