If you are having an issue logging into ClassLink you can try resetting your district setting.
1. Start the ClassLink app then click the arrow in the top left corner.
2. On this new window select "ClassLink Launchpad" in the top left corner.
3. You will be taken back to the default system login page. Click the arrow in the top left corner again.
4. On this screen click in the search field at the top of the window and type in "Grapevine". This should limit the list down. Select "Grapevine-Colleyville ISD" from the results.
5. You should be taken back to the GCISD login page where you can try logging in again.
If you are still having issues logging in please submit a support ticket. Include as much information as possible, especial the name of the user trying to log in.