New owner looking for information/help.

Hello Reditors! I recently acquired these 2 machines from a buddy who no longer had room for these or the drive to learn what was wrong/fix them. So I've come here to start my journey amd ask for help! I have keys for both games, the Cherries has an extra "skeleton key"( what my buddy called it) also.

When I powered up the Cherries 🍒 it had a call attendant flashing( for hand payout). I cleared that with the Jackpot key(I think) then it had a bill acceptor error(I think it said) ran out of time to mess with it that day so I powered off, but came back today and powered up and no codes at all. But it's not accepting any bills I insert to add credits.

I have not powered up the sizzling 7s machine yet. My buddy said it powers up fine. I have only opened it and pulled the hopper out and got some quarters unlocked from there. (Hopefully that was the only issue!) I'll mess with that later today.

A few basic pictures of the machines attached. Any advice/direction on where to go learn more about these games would be greatly appreciated! Thanks in advance!