Relations factors into the probability, as does your threat, treaties, other diplo stuff, same continent is a +, land route that doesn't need convoys is a +, size of trade (bigger is better), their money pile are some of the general factors, then the country-specific routines may or may not have other modifiers. Them buying from you uses their convoys, so if they have none free it'll be impossible (although annoyingly often they'll buy and somehow end up with not enough convoys and the trade will sit there with the stop sign for a while until it cancels). The big killer is they usually won't buy something they're already selling, so if sometime in the past they sold 1 spare energy to someone they won't buy yours 'til they figure out they're short and cancel that trade, which could be awhile if they have a big stockpile.
Sometimes with no apparent change they'll be willing to buy/sell in a few days, so keep checking - they may have accumulated enough money to feel better about spending their income, etc.
Sometimes with no apparent change they'll be willing to buy/sell in a few days, so keep checking - they may have accumulated enough money to feel better about spending their income, etc.
