My zyxel router used to

Question

My zyxel router used to work on my PC, all my laptops, my ps3 and my wifi enabled phone. but when I went on the Pc and my mum went on the Laptop it wouldnt connect.It only connected to one thing at a time. a man came to fix the problem and when he was away I found that the problem persisted and not only that it wont connect to the ps3 or my phone at all now. Any Help or suggestions