Well, we need photos. And, I suspect your little tree might be a bit root bound since it's in its original pot? Lastly, how well are you watering? Over or under watering can cause blossom drop, as can not enough light. Photos will help us better diagnose your problem :-)

Patty S.

Last year I received a calamondin tree for my birthday. It flowered throughout the autumn and produced twelve wee oranges. This year, the tree has doubled its size and is loaded with blossoms since May. They will not open and many are turning brown and falling off. The tree seems healthy and does not shed leaves.
I am uploading a picture to help diagnose my problem.
Thank you........

For some reason the picture did not upload. I downsized it, and am trying again.

same with mine, I have had mine for 9 years and its doing the same thing, blooming, blooms turn brown, however there are tiny oranges once the flowers fall off or if they get old looking i take the flower portion off and I do have a mini mini super tiny orange under them. My cat DID tip it over and broke the planter, so im uessing mine is just in shock. the strangest part is - Mine LOVES it outside!! i have tried to brong it out three times. wheni do the leaves curl and droop. it has proper water, and fertilizer. but it is telling me it is hating this summer! ( odd) . so i keep bringing it in and putting it in its winter spot with the grow light on it and it seems happy, but still will not open its flowers. any answers will help!

Are you feeding it with liquid citrus food - diluted - about once a month... because it is in a pot?