Q.My Camellia Has A Few Yellow Leaves And Did Not Flower. What Do I Do To Help It?
It’s in partial shade and flowered last year but I did not prune it.

Certified GKH Gardening Expert
It is under some kind of stress. It's time to fertilize with a product for acid loving plants if you haven't this year. That should help. Did you have a late frost? Bud mites are a possibility, too, as well as too much or too little water. Pruning is not essential but more to thin the plant or shape it, so that shouldn't be an issue.
These articles should help pinpoint the problem.
https://www.gardeningknowhow.com/ornamental/flowers/camellia/camellia-fertilizer-info.htm
https://www.gardeningknowhow.com/ornamental/flowers/camellia/camellias-wont-bloom.htm
https://www.gardeningknowhow.com/ornamental/flowers/camellia/caring-for-camellias.htm