I'm having the same issue.  Ruined the game for me.  I had purchased 8 of 8 gold from an ally.  Actually, I had bought all of every resource that ally had. Then, suddenly, I had 0 of 8 gold and had to rebuy them.  But, buying them would just take the money and not give me more gold.  So, this is multiple bugs.  First, I shouldn't have just randomly lost access to all resources I was buying from them when there was no pillaging.  Second, I should be able to rebuy them.  Third, if I do lose access, there should be a notice so I can address the issue rather than not noticing for several turns.  Please fix.  The game is basically unplayable without being able to buy resources.

While we are at it.  I noticed on the main screen that some of the resources at the top of the screen had a red background and a little red dot.  But, I can find no explanation for what that means.  Please explain.

I've encountered this bug as well intermittently, where the trade goods I just bought would reset to zero leaving me without the goods and the money I spent.

Bumping this.  I checked after the latest patch and my game is still broken for trade.  When I buy the copies of resources, it takes my money, but doesn't give me a copy.  It seems like it stopped providing the resource copies to begin with for no reason. Further, what are the little red dots next to the resources at the top of the main screen?

Same.  I'm unable to buy Incense from Black.  When I try, the route disappears again.

Italians Turn 120 - No Incense from Black.ctr

Hello!

We are aware of the situation and investigating a solution, your saves will also be included to our bug report. At the moment we do not have a workaround for this issue. 

Sorry for the inconvenience and thank you very much for taking the time to send us your bug reports.

​This has ruined the game for me along with two more bugs. I find it extremely embarrassing that the development team continues without fixing these bugs when dealing with very serious bugs, since it makes it impossible to play. Worthy of getting my money back!

Facing the same issue and it's literally killed my desire to play the game. Can't believe this has been a "known issue" for a year and nothing's been done about it...