The only tip I have would be not to make it too complicated. Set your router password to something realy simple for testing purposes such as… TEST1234 and/or test1234 and reboot it, set the Humax to the same and reboot that if necessary. If it works then change the password back to whatever you want and test again. If it doesn’t work then let us know which router model and the type of encryption the router is set to, i.e. WEP, WPA etc. etc.
I’m assuming the Humax is in a place where it can receive wifi? If you use wifi for any other devices such as phones, tablets etc. then you should be able to download a wifi app which will indicate the signal level from your router, if possible it may be worth checking that you can get a decent signal all around the Humax.