Thunderbolt display not charging MBP battery

I just did what AdamJ said, took my magsafe adapter off and clean it up with a toothbrush to remove dust. It really worked and now my thunderbolt display is charging my macbook pro! :)

I had the same problem here. Reset the SMC and it fixed problem for ½ a day. Then back to not charging. Although the Macbook Pro indicator did show a charger connected, it just wasn't charging the battery and there was no light (amber or green) on the magsafe power from the Thunderbolt display. Another magsafe external charger gave the same results. Swapped the little magnetic magsafe adaptor with my wife's magsafe adaptor and now the light glows amber and my Macbook is charging again.

I've just recently started having the same issue with my 27" cinema display and a MacBook Pro (Retina, 15-inch, Mid 2014). Flipping the magsafe adapter didn't seem to work consistently for me. Plugging in the regular power adapter worked fine.

For me, cleaning the contacts with some isopropyl alcohol on a q-tip seemed to do the job. Might not be a long-term solution but so far it's doing the job.