Simplify3D User Forum

I apologize for using this forum, but I’ve searched everywhere else for an answer.
Trying to send gcode commands to my 3d printer (Reprap knockoff). Some work, but others, such as M851 and M212, reply with “unknown command”. I looked in the Marlin fw site, what I am using, and found a couple of references to the fw settings that need to be enabled, which I already have correct. What am I missing?? Thanks for any assistance. I have tried this with a couple of different slicers with the same results. Running the latest Marlinfw bugxfix. I figure it has something to do with the fw settings, but I have tried everything I can think of.

Can you show examples of the actual syntax that is failing?

Thanks, but got it resolved. I was not aware that each printer version has potentially different/unique gcodes available. I downloaded the ones specific for RepRaps and all is good.

I figured that may be an issue. Good to hear it is resolved.