There are many answers to this question, as I will list below.
# The speaker could be faulty
# A(some) wires can be loose or cut in between the speaker and the CPU
# Some apps will only support headphones
# High volumes on a some speakers may damage the speaker temporary or permantly
Here are some ways the the problem can be fixed, or resolved.
# Doing a soft reset
# Doing a hard reset
# If the tablet froze unplug it untill it dies, then turn it back on (this my take form a minute to a week, matering on you screen brightness or/and how much battery is left)
# Push the reset button
If all fails,
# Bring it to a servive guy and see how much the repairs will cost( if the repairs are more expensive then the tablet itself, get a new one)
# Find a speaker that you can mount on the back of the tablet that connects using a 3.5mm headphone port or a speaker with an adapter for a 3.5mm headphone jack
# (only recommended if you give up) Find an awesome way to destroy it (for ex. mounting it with ropes on 2 of your cars and ripping it to pieces or do some target practice and shoot it with something like a 22)