If you've received a likelihood of confusion refusal, it means the USPTO is considering your mark confusingly similar to an already registered trademark, meaning similar to such a degree that it could potentially cause confusion in the market.
Similarity is a complex concept within trademark law, as what makes two marks similar or dissimilar is not always straightforward. The examining attorney will look at several factors, including visual similarity, phonetic similarity, similarity in goods and services offered, etc.
While likelihood of confusion refusals happen often, resolution is not always easy. Your chances will depend on the nature and severity of the similarity. If you received a likelihood of confusion refusal, it's highly advisable to discuss the next steps with a trademark attorney.