Out of curiosity, have you tried talking with your district techs? In particular, whomever manages Canvas for your district. That level administrator might have the ability to either look up the password, or manually reset it. This information is what they would need to look into: https://community.canvaslms.com/t5/Admin-Guide/How-do-I-manage-a-user-s-login-information-in-an-acco...
If they do have that level of access, they could reset the password for the student.
In regards to not receiving the emails, that is most likely one of two issues. Either their email address is not correct in the system, or your district's email filters are somehow filtering it out. The first one can be confirmed by the person I mentioned above with admin access (the steps on the linked page can help get them to the right spot and possibly fix). The second one is something occurring on your district's end in your email system, so would require a district tech to look into the Spam/Junk mail filtering to help fix.
Not sure if either of these are the things you have looked into, but would be the first things I thought to check.