Welcome to Android Central! Can you give us the exact model name/number? Try powering off by pressing and holding the power button until the screen turns off--you might have to hold it for at least 10 seconds. After it's powered off, try powering on again.
If that doesn't work, you might be out of luck. Budget tablets like these have a higher chance of hardware or firmware defects, and they also have minimal support. You could try contacting their support, but I wouldn't be too optimistic:
Get Support | RCA Tablets