UK lender Nationwide Building Societys customers were unable to access online banking and a mobile banking app on Sunday after a scheduled overnight maintenance overran. Nationwide spokeswoman Michelle Slade said that the online bank and mobile banking app were now back up and running. Unfortunately our overnight planned maintenance has overrun and is affecting customers accessing our online bank and mobile banking app, the customer-owned lenders spokeswoman said. The customers of Britains third-biggest provider of mortgage and savings products complained of the online banking glitch on social networking site Twitter.