Bypass the login screen with registered users and private mettings

Hello, I'm using the Zoom API to integrate it into our eLearning website. From there, I create a meeting [users/{$hostEmail}/meetings] with the following options:
'host_video' => true,
'participant_video' => false,
'join_before_host' => false,
'mute_upon_entry' => true,
'auto_recording' => 'cloud',
'waiting_room' => false,
'approval_type' => 2,
'meeting_authentication' => true
Then, from the API, I also create the student accounts [/users] with the option: 'action' => "autoCreate"
I retrieve the start_url for the teacher from the class creation process, and the teacher connects directly from that URL. I'm retrieving the join_url for the student connection, but it always asks for a username and password.
How can I bypass the login screen and have the student join the meeting directly?
I've tried creating a ZAK for the student and passing it to the join_url, I've tried using a user token, I've tried accessing with ?tk=;
I've also tried using the client-side web SDK by creating a signature and running init and join, but in all cases, the login screen pops up.

I need to register users with the same name we have on our platform because we then retrieve [report/meetings/{$meetingNumber}/participants] the participation of each participant and we need to create reports with this information.

Thanks, any suggestions are welcome.