As stated above, buy the tea, LOAD the tea in your hold, Verify that the tea is in fact INSIDE your hold. Before you leave the station, check it one more time, then proceed to the end stop, open the mission and sell the tea.
Why do I emphasize ensuring the Cargo is loaded? Long, long ago in a system about 65 lys from my now home system, I was a young and inexperienced Commander. I took a job to "Take Widgets from station A to Station B", didn't even have to go search for the Widgets, they would give them to me. So I took the job, Hot-footed it out of the station, jumped to the next system, landed at the end destination, pulled up the mission...and No Widgets. Hmmm...
Fly back to the start station, open the job, Yup, there are the widgets, Hot-foot it back to the end station, open the mission...No Widgets. WTH?!!?!?!?!
Fly back to start, open mission, Yeah, there be Widgets here...Think, "Wait! Maybe I have to buy the widgets in the market". Go to the market, buy X amount of widgets, blast off, get to the end station, open the mission....NO FREAKING WIDGETS!!!!!! ARE YOU KIDDING ME??!!?!?!?!!!
As I was in a Sidey, I had filled my hold with Widgets, so I had to sell those widgets (at a loss), and fly back to the start point.
Fly back, land, open the mission...and then I noted the button to LOAD the cargo...Ahhh...I realized that just accepting the mission didn't automatically load the required cargo . So I hit the button, load the cargo, and finish the mission. The payout barely covered my total fuel costs and the loss I took on the other widgets. But I learned a valuable lesson.
1) ALWAYS read the fine print of the mission...ALWAYS. You could be biting off more than you can afford to lose.
2) SLOW DOWN! While space truckin' is a blast, you can miss something important if you are flying like a ninja with your hair on fire
3) If you repeat something and get the same exact WRONG results, you have missed something and should refer to rules #1 and #2.
Hope that you got your problem worked out. Elite Dangerous has a learning curve at times like trying to climb Mt. Everest with a 100 lb pack on your back while wearing cement boots. But in time, it will become natural and second nature. But, even the Commanders who have been here for years still learn a thing or two from time to time!
See you in the black Commander! o7
Michael Charlie Golf signing out...