Maybe first enter your wallet address into
http://chain.nem.ninja/#/blocks/0 there is a search bar at the top after entering this you can view the balance of that address and if your funds still show up on the chain it wil be a problem with either your internet connection like a firewall or other things to do with your setup I would guess
I have followed your guidance but cannot see the coins. No transaction shows up when I enter my wallet address. What should I do? Is my coins lost forever?