If the Main Hall is being/always shows as being upgraded and any culture buildings and the builders hut not having hands above them would show that there is nowhere left to help - if the village is small the owner may have quit and left it with the Main Hall upgrading and unless they log back in then it will never be finished. The builder has 2 to 5 slots, depending on the level, once the slots are full then it is no longer possible to help it, if the culture buildings have all been polished, then again no hands and its not possible to polish them until the current timer on any culture building runs out.
If you can't help them then its not your fault, if they're active then the Main Hall will finish upgrading and you can help again or maybe you get there before another person polishes a culture building. If they're inactive then there's not a lot you can do until the 30 day purge of inactive villages, the subsquent gold mines for collection and then followed by new neighbours.
