I have a miracle berry bush (Synsepalum dulcificum) and its leaves are dry and brittle. I tried to water it, but it does not seem to be responding. Should I presume it is dead and get a new one?
From your description it sounds like it is dead. The best way to determine if it is still alive is to scratch off the bark of a small spot to see if it is green underneath. If it is green underneath the plant is still alive. If is brown then the plant is dead. You should do this test in multiple locations. One part of the plant might be dead when other parts are still alive.