M+ & Jam combo: Step Sequencer isn't looping over 16-bar.. playhead just goes on indefinitely.

BUT…… when I connect the Midi 5-dinn cable from the MX-1 "out" to the Maschine Plus "in" and then change the Midi settings on the MX-1 to "receive" I am unable to get the play/record button to work.

This doesn't make sense unless you're saying you can't get play/record on the roland to work.

Pick one device to be the master. If maschine is receiving midi clock, it's also going to wait for a start command. That's normal. You'll need to send midi out of maschine and IN to your roland if you want maschine to control the master clock. In that case, you'll need to hit start on maschine and not on the roland.

You may want to consider switching to ableton link instead of midi; but I don't think the sp404 does ableton link.

I struggle to think of a scenario where having the sp404 connected would cause the issue. Maschine is going to loop the current scene if you're in ideas view. Even if you have it set to receive clock; it wouldn't be able to keep playing. If you had it in song mode and didn't have loop on; your play head is going to keep going. If maschine is receiving clock from a device that sends song position; it might try to loop back when the device sending clock tells it to loop back. This could cause issues if you have maschine set to loop a section that's a different length.

Are you in song mode or ideas view? If in song mode; do you have loop on?

You can toggle looping in song mode by pressing shift + restart (loop). Press and hold shift+loop and you get a couple of options at the top.

If you're in either ideas view or song view, pressing the [IDEAS (Song)] button just places focus on on that view. Imagine you're in pad mode and press mixer. It just switches focus to the mixer. The [IDEAS] button does the same, but it's going to place you in the view you currently have active (either ideas or song). Press [IDEAS] once to enter the view. Now hold shift. Buttons 1 and 2 (above your left screen) will let you toggle between ideas view and song view.

If you're not already familiar with maschine; seriously consider learning it while using the software if possible. You don't need a very powerful computer or anything. Being able to see the software is going to make things make soooooo much more sense. I understand you may have bought it to use standalone; but seriously; it's so much easier when you can see what you're doing. IMO, that's going to make learning it (and troubleshooting) a lot easier.

For example; if you were doing this in the software,you would have seen the loop button was off. That would then push you to figure out "how to turn on loop from the hardware"