On a G20, in a casino environment, there is a big metal cover that offers "security" for money in the cash can (stacker). This cover is the first thing that goes into the trash when 2nd hand dealers get machines ready for resale (there's no need for it in an unregulated environment). On most G20's, there are 2 break points in the "S" loop. One is on the side or bottom of the DBA (Dollar Bill Acceptor) which is for the door in front of the cash can (if your machine still has one). The other is on top (bottom - since it's mounted inverted in a G20) of the Cash Can. This top (near the Upper right cooling fan) "break point" in the loop is usually jumpered because in most jurisdictions, the Cash Can "security" door meets the "security" requirements. Other jurisdictions require 2 doors (2 keys) just to get the Cash Can out of the machine. I'd check the other break point which will be under the printer or behind the DBA (Fun Fun removing everything to find it).
The wires in the "S" loop are G (green) and R/G (Red with a Green tracer). Maybe take a flash light and see if you have see any hanging wires, that came untwisted or pinched, under your printer before you remove the printer and DBA frame. Or hopefully it came untwisted or pinched near the upper right cooling fan area.
Hope this helps....