It was working fine but now will only tick for a few seconds at a time. What to do?
look on the internet for either local antique shops, or clock shops, or clock repair. You will probably have to take it in to one of these places. If it is real old it might be dirty inside and needs cleaning to make it work smoothly.
I have a grandfather clock that is 122 years old. In the past it needed a clock repair person at least 4 times that I know of.
Good luck. Oh, and don’t fool around with it yourself, you might do more harm than good.