A hard reset will correct many Chromebook issue. According to Google's site, this might erase files stored in Downloads on the Chromebook. It won't affect things saved in Google Drive or Classroom.
Step 1: To perform a hard reset on a Chromebook, hold down the refresh key and tap the power button. You might have to hold down the refresh key (but not power) until the device restarts.
Step 2: If a hard reset does not work, you might also need a policy refresh.
Log onto the Chromebook and go to chrome://policy.
Click the "Reload Policies" button.
Wait 60 seconds.
Restart the Chromebook. You can hold down the power button until it shuts off, then turn it back on.
Log on and test it.
You might have to repeat steps 1 - 5 a couple of times.
If this does not solve the problem, please fill out the Chromebook Support Form and indicate that you did the reset process.