Based on your description, I understand that when you deleted a user, you filled in "Give another user access to OneDrive files", but not filled in "Give another users to email".
1.When you delete a user for the first time, you can choose "Give another users to email" because the user has a license.
After restored a deleted user, you need to assign license to the use again, then when you delete a user for the second time, you can also choose "Give another users to email".
2.To restore a user, go to Microsoft 365 admin center -> Users -> Deleted users -> Select the user -> Restore user.
After restored a deleted user, if you cannot log in, select the restored user in the Active users, reset the password, then try to log in again.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.