From a fault finding point of view, it doesn’t matter the left and right bit.
First thing, when you press the credit button, does the Credit reset RE energise?
If No, then with a DMM set to Ω and the power off, check for continuity from the thick common wire and the White/Orange wire at the credit button. If this is OK, then check for continuity from Black/White wire to Credit Reset RE Coil. You can check both sides of the coil; you will get different readings but still closed circuit.
If all this checks out OK, then check the credit SW for continuity when closed too.
If the first test fails, the issue is likely to be at the Start RE or Jones plugs ETC. If the 2nd test fails then you can break that side of the circuit in ½ and test again.
You are looking for Continuity from the common wire (left side of the above image) to the Coil power supply wire.(Right side)