Answer: These trees need to bloom in order to set fruit. If you are pruning often you may be removing the blooming wood; pruning hsould only be done in late winter.
They also need very bright light combined with cool to average temperatures in the winter time. Fertilizing with a fertilizer for acid loving plants may also help, applying it from January through September but ceasing for the winter then the plant naturally slows its growth. Make sure you are not overfeeding as this can lead to an overabundance of foliage in preference to flowers.
Finally, it can take some varieties several years to come into production, so it may be that patience is the key. Good luck with your lemon!
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