(How not Hw, sorry can't edit subject line)

I play the sandbox (Zeus) and started with a vassal city, Miletos. Unlike my colony, which does pay, Miletos does not pay tributes. The city info shows "paying tribute ... suspended". The Manual says:

"Vassals and colonies will pay tribute to you every year unless conquered by a rival, or unless the leader becomes so annoyed with you that he suspends tribute payments or even rebels against you."

Miletos is shown to be "dedicated", the history only shows two thumbs up, no thumb down. trade with Miletos is in good shape, no trace of any rebellion. So what can I do to stop the suspension? Attack is not possible (button not clickable, probably because there is no rebellion).

Reading the manual, I think there are two ways to get them back to paying:

1) Improve...

a) relations directly. Gift them money or goods they need and hope that the mood rises enough.

b) relations with other vasalls (colonies? - the manual speaks of same "kind of city", not sure if colonies and vasalls are counted towards the same group), This should also help with the one not liking you (but that will be only possible if you have more then 1; you can try with our colony, but as said I'm not sure if this will count)

c) relations globally by winning cultural games, hosting them or devoting yourself to Zeus (indirectly Apoll is a good choice as well, as you are more likely to win the cultural competions)

OR

2)...wait until they start to rebel, then invade and win...what will make them resume paying tribute. You can try to make that happening faster by further angering them...but if you invade, don't pillage them...because that will likely let start the new relations poisened again...

Thanks! ...done all that, I now got 7 thumbs up, no change.

Zeus' temple is still in the making.
I'll post again if it makes a difference. Not a cheap solution anyway :-)

About forcing a rebellion... makes sense. I'll not try it in this adventure, but next time I encounter the same problem.