Ok, so, you CAN'T add play credits to the game if you don't have any to start with (i.e. the dollar bill slot is showing on the machine)
You MUST *unlock* the catcher, THEN send the code to modify play count. The problem is you are trying to write an invalid value to the unlocker (probably)
Unlocker GW Code:
DD000000 00000240 -- button combo (skip this)
D3000000 3646673C -- unlocker address
20000000 00000004 -- write this value to "unlock" the machine and add 5 plays (it's like you put in a dollar)
D2000000 00000000
After taking forever trying to find how to set up button triggers for commands on NTR, I ended up on a forum thread in spanish, where some people were sharing NTR cheat plugins. Downloaded the source for cell9's ALBW cheat plugin and changed it to run WRITEU32(0x3646673C, 0x00000004); when L+UP were pressed.
Happy as fuck thinking it was finally going to work, I put it in the right folder(/plugin/0004[...can't remember]). Ran Badge Arcade, confident my suffering would end, only to be met with 006-0114 when trying to connect to Nintendo Network. "Oh right, I read somewhere that NTR disables online services when you're using cheats. Is that true?" Restarted the title to be sure. Yeah, same error. "Well fuck."
Deleted the plugin and went back to the debugger.
"Maybe writing something to 0x364674C is affecting how 0x364673C is interpreted. It might only unlock it if I exclusively write 4 to 0x3646673C. Let's try that."
So I tried to understand how the array that write() receives is read. Passing just an int(0x04) to it didn't work, since it was expecting an array. (0x04) doesn't work. I assume the 0x00 in (0x04, 0x00) is just a terminating null value, the likes of which you see in C strings. I opened Badge Arcade with NTR Debugger enabled and connected to the PC client. write(0x3746673C, (0x04, 0x00), 0x0000002e) -> no dice. No change whatsoever from the previous behaviour, the catcher is still locked, while I'm offered to pay for a few plays.
-- EDIT --
WHOA! Some black magic happened. I was at the catcher, minding my own business, accepting the fact I wouldn't cheat the rabbit tonight, when I pressed A to get the "you don't have sufficient funds in your account" message. At that moment, I ran write(0x3646673C, (0x04, 0x00), 0x0PIDHERE) one more time. No change, but after I hit "Cancel", I had 15 plays(I set it to purchase 15 plays at a time, so maybe? I dunno).