If the people you have invited show as ‘pending’ then that means they have not yet accepted the invitation.
This may be because of several things:
1) They haven’t yet opened the email and accepted.
Ask them to open the email and accept.
2) They didn’t receive the email and it may be sitting in their Junk/Spam folders. Get them to check those folders.
3) They have deleted the original email or it never arrived. In this case just invite them again.