Citrus trees have some tendency to alternate bear with heavy crops every other year. Water, fertilizer and plant stress management can lessen the severity of you on year/off year cycling. A complete absence of flowering following a year of heavy production is likely because your fertilizer rates are too low. I would consult with University of Arizona citrus production fact sheets to identify the appropriate rates of fertilizer for your age tree. Cold temperatures, extremely hot temperatures, or dry soil during the budbreak and bloom period may also cause reduced fruit production. In my experience, most people are under-feeding their citrus tree, so that they need a year off to recover from a heavy crop. In Texas, a tree the size of the one in your photo should get approximately 6-8 pounds per tree of a 13-13-13 type fertllizer each year. That total amount is divided into 2-3 feedings--February, May and June. Use the 8 pound rate if there is a big crop, but drop back to 3-4 lbs if you have no crop. The message is feed more with abundant fruiting and feed less with absence of fruiting. In this way, alternate bearing severity should be less. However, consult with University of Arizona information, since your climate and soils are different than Texas.