Dark ipad

Have you tried a simple hard reset of your iPad by holding down both the Home and sleep/wake buttons simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons?

Good Luck!

If you are unable to increase screen brightness in settings, you likely have a screen which about to go bad. If you are actually using an iPad on iOS 10, you have a very old iPad, which means it more than likely time for a newer iPad.

Have you gone into the Settings app under the Display & Brightness settings and toggled OFF Automatic Brightness?

What iPad year and model do you own?