Another day , same mission (buy tickets of "pot o plata") and same error can't buy tickets 

Need more info here Zendel, what are you experiencing when you try to buy tickets?

When I click on "buy bronze ticket" or "buy silver ticket," the green button darkens as if it's being purchased, but it doesn't actually buy anything.

The other day I had a mission to buy several tickets (I think it was six), and after many attempts, I managed to buy three. However, the mission still indicated that I had bought all six and showed as completed.

Today, the mission was to buy one ticket, but I haven't been able to, even though I've left and re-entered the casino several times.

Do you have cash in hand?

Yes, I had cash when I tried to buy the tickets