Can not receive the email of reset password

I invited one user to be a member of the organization. He received the invite email, but can not receive the reset password email. After try to login auth0 multi times, the account is locked. On your web site, I found two solutions to figure out. One is waiting for 24 hours, it doesn’t work. Another is “forget password”, we tried many times but no email received.
Can someone give me some advice to figure it out. Thanks a lot.