One or more students are missing from an imported classroom

There are 2 possible reasons a student did not get imported from a Google Classroom:

Student is not in Google Classroom: 

Make sure that the missing students have been invited to the classroom, and have accepted the invite. After any missing students receive and accept the invite, go to the Classes tab, find the classroom they're missing from, and click "Add/Re-Import Students". Sign in with your Google account and select the Google Classroom they're a part of, and click Re-Import.

Student has a Teacher Account: 

The student also may have created a Teacher Account already. If this is the case, the student should log in to their account, go to Menu, then My Settings, then the Membership tab. Then the student should click "Delete Account" to delete their Teacher Account so that they can be imported as a student. Then re-import as above.

Student cannot sign in with Google

Make sure that the student actually has a Google account and not a Boom account; Google accounts are signified by this symbol next to their avatar:

Also, make sure that the student is actually clicking "Sign in with Google" and not "Sign in with Boom"

Students who have forgotten their email or password will have to go through Google's account recovery process to get their accounts back.

If nothing happens or the page freezes when the student clicks "Sign in with Google", it is likely the student's browser is blocking popups or third-party cookies. Allow both popups and third-party cookies from to fix this. For managed devices, your IT department may need to allow Boom Learning login and whitelist the domains listed on this page.

If the student gets the error "Please wait for your teacher to finish setup", the teacher most likely needs to re-import. See "One or more students are missing from an imported classroom" above.

Can't add new students to an imported classroom

See: Adding New Students or Sign In With Boom Students to a Sign In With Google Classroom.