What are you using for leavening? Baking soda and baking powder lose their power if they get moisture. Baking powder is worse. I use sourdough so I don't have to wonder if it will rise but it takes a little extra time.
You can check baking powder by putting a bit in a saucer and add a little water. if its good it should foam up right away. do the same test with baking soda but use lemon juice instead of water. If they pass the test, timing or working the mix can give bad results. Try adding the leavening after the rest of the dough is mixed or try not to mix or knead as long. (I have assumed you are making rolled and cut biscuits)
You can check baking powder by putting a bit in a saucer and add a little water. if its good it should foam up right away. do the same test with baking soda but use lemon juice instead of water. If they pass the test, timing or working the mix can give bad results. Try adding the leavening after the rest of the dough is mixed or try not to mix or knead as long. (I have assumed you are making rolled and cut biscuits)