This could be caused by several different problems.
1. Make sure that it is charged.
2. Check your WIFI connection. Go to the lower right hand corner and click on the wifi icon (looks like a funnel)
3. Make sure that is says "Mananged by DISD" during log in.
If you can't log in, remember that you have to enter your ID number @dallasisd.org. (firstname.lastname@example.org)
Your password: (if you forgot your password, see the section on passwords)