Is there a valve on there somewhere, possibly on the loader that isolates the loader from the 3 point. That***8217;s how my L245 was.
I have a L5450 and no experience whatsoever with any other models, but on the 5450 if the rear hydraulics are engaged, such as when I am using my wood splitter, the lift arm is disabled. I have never tried engaging the rear hydraulics control without first attaching the wood spitter, so I don't know if the lift arm would be disabled, even if the hydraulics are not circulating. Which would be the case if the control calls for rear hydraulics but no implement attached; I think.
Since you have just started learning your machine, do you know if it is equipped with rear hydraulics? If so, that is the first thing to check. I imagine it is something simple that you don't know to check until you are more familiar with it.