Follow these steps to see if it works:
On your iPhone:
You can also try the My Wi-Fi app as described here, but you may need to be connected the Wi-Fi for it to work.
If the SSID from your router is not visible to your iPhone, it will have trouble connecting. Make sure your router settings are not set to hide your SSID.
If you know the SSID of your wireless network, you can type it in to your iPhone, along with the password and connect to your network.
Your computer will use somewhat different methods to connect to the network, and may well work even if the SSID is hidden.
Would you put that in plain English for me...my 80-year old brain doesn't do computer talk ! So...I know what my WiFi network should be...how do I see if my router (is that the same as modem?) is blocking my ...Network? If I just need to type in my network number, where and how do I do that ? I'm sure it's something very simple...just not making sense to me.