Q.Key Lime Tree’s Fruit is all seed inside-no juice
Hi My Key Lime tree (or at least that is what the tag stated when I purchased it) has been in the ground for over 9 years maybe even 10 years. It started producing fruit about 4 years ago. I kept thinking I was checking the fruit too late in the season and the fruit had gone to seed. But for the last 2 years I have been checking them earlier & earlier. The inside of the fruit is nothing but seeds, thick skin, no juice at all. It is sticky and smells like limes but that is all. The fruit is mostly round and very hard. The tree is 12′ tall and has 2″ thorns on it also. Is this tree ornamental maybe? The seeds grow easily. I must have 40 babies growing from the fruit I just let drop to the ground.
Thank you for any answers you may be able to give me.

This is, most commonly, caused by too much nitrogen, or a lack of phosphorus and potassium. This can be fixed with the addition of potassium and phosphorus. You can also fix this with increasing soil pH, but this is a little more risky, as it can cause adverse effects with acid loving plants. The best thing to do would be to add phosphorus and potassium raw, or as potassium phosphate, or other flowering fertilizers. It is also handy to have dolomitic lime and iron sulfate to add once or twice per year. This will keep everything conditioned at the root zone.
This article will give you more information: https://www.gardeningknowhow.com/edible/fruits/citrus/citrus-fruit-thick-rind.htm