There is less gluten in sprouted grains and therefore, it can be tricky to get a good rise out of the grains. Gluten is broken down as the grain malts and the starches are converted.

Are you sprouting your own grains? If so, you may be over-spouting them. If the grains sprout too much, they will no longer have enough gluten or starch to give a good rise. Most people find that 1/4″ - 1/2″ sprouted yields the best results.

If you are purchasing your sprouted grains (or if you do them yourself), purchase the whole berries and only grind in small batches when needed. This will keep everything very fresh. If they are too old, your results will be sub-par. Check in with your supplier, if you purchase your berries/flour, and make sure they are ensuring the highest quality and grinding in small batches (so it’s not sitting around in a warm warehouse before you get it). Also, be sure that you are grinding as finely as your grinder allows when grinding your own berries. finer flour usually produces a less dense loaf.

Lastly, a little culture never hurt anything and can also help the rise in many ways. Many bakers (sourdough or otherwise) swear by adding some milk kefir, yogurt, water kefir or other culture to their dough as part of the liquid in the recipe.

Hope this helps some! Good luck! I personally love sourdough and have had nothing but superb results with it. If you want to give it another go, I highly recommend this Sourdough eCourse at GNOWFGLINS. It is very thorough and the videos are invaluable.