My Game Makers don’t have coin hoppers, but I might have a couple of suggestions. Sorry if I’m pointing out the obvious.
Does the hopper function correctly when doing a Hopper Test in the PIO Test menu?
When you configure the machine there are two options for “Hopper Type”. Coin and None. Ensure Coin is selected.
When you configure “Hopper/Credit Limits” maybe ensure none of the options is disabled and max them all out or perhaps disable them so there is no max credit limit. Since I only have printers and no hoppers I simply disable everything. (One, I can’t remember which, I wasn’t allowed to disable so I maxed it out.) Not all the options will affect the hopper.
I don’t have any suggestions if it’s a mechanical issue.
As far as TITO goes – I’d like to have it myself, but there is no option for this. There are some TITO tweaks out there to buy and add to some machines, but they are not compatible with the Game Maker.
Sorry I couldn’t be of more help.