Send an email to your Yahoo email address and wait until you receive an error message. If you receive a message indicating that your email has not been received, it may be mentioned that the account is deactivated.
If this is the case, you can contact Yahoo to find out why your account was deactivated. To contact them, click on this link. Select Account and enter your Yahoo email address. Then select Contact a Yahoo specialist > Abuse and spam > Got a message my account is deactivated > Email a Yahoo specialist.