Trouble logging onto admin

I have just taken over admin of our Word Press websites and for some reason the log on details for one of the sites isn’t working. When I tried to reset the password using the previous admin’s email address, I got the message “Password reset is not allowed for this user”. I know nothing about code so the other posts in the forum are pretty meaningless to me. The website in question is http://www.micropowergroup.com.au. I haven’t had this problem with the other sites I’m managing so would appreciate some help. Thanks.