I don't know about the tool offset button.
For the run from here -
Try the set next line button first.. The problem is, Mach has, on a restart to start at a point where it knows what it is, and which axis it is moving. I don't know Mastercam, but if it ignores the G1 (or G0) commands, and merely lists the moves on each line, then Mach will be a bit stuck understanding which axis to move and where.
If you pick a line, with "Set next line" that contains a full instrcution, then pick "Run from Here", Mach should run.
I use the demo version, and this runs the buttons properly, as I say, once you have picked where to start.