Hey guys,
I may have stumbled upon a solution, I was having this same issue and was annoying as hell, so I tired to google it and didn't find any answers except for this thread..
I thought maybe if I plop another train station just to get rid of the pesky messages reminding me for a second station. So I did it, and voila! tourism returned in a second,
from loosing -1400k to +22k
not sure if plopping another bus depo or ferry would work if overloaded, but it worked. Possibly the stations were so overloaded, sims didn't want to get off and flipped my city the bird before leaving.