Due to GDPR it is not possible to redownload the login slips. Please check to see if you have the login slips downloaded on your device they are called:
Doodle_login_details
Doodle_login_slips
Doodle_login_cards
If you are not able to access these you will need to regenerate the login slips. If you do this it will reset the students' passwords and so they will not be able to login with the password they were using before.
Please see here for the steps to take to regenerate the login slips.
If you are having problems downloading the login slips, please make sure you have enabled multiple downloads on your device.