Hi @Sanjeedabd! Welcome to the Community!
Those invitations will have expired by now (they last 7 days) so you will need to re-send them. I recommend you send them to the specific GitHub usernames you want to invite, rather than to email addresses.
Each collaborator should confirm that they are logged into the specific account that has been invited (and no other GitHub account) before they try to accept the invite. They might want to log out and log back in again to refresh the session before trying.
Can you also ask them to check whether they are currently using any sort of browser extensions such as ad blockers that might be interfering with the page? Could you ask them to try temporarily disabling extensions and trying again please?