I tried to set-up wireless and the provider is DSL not able to connect through Ethernet nor by wireless, it happen 3 different places. 
What should I do differently?
Any suggestion tech gurus? Thank you.

What kind of Wireless Router are you using ?

It worked perfectly with Com-cast and it is eHome wireless router but unable with DSL.
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Well Check Your Setting once again if you have guide for that wireless router it will help you to get it working faster . Your main Line is connected to Modem in first place ..Things you will need to do is :
1. You should connect wire to wireless router that connects Modem and your PC with Landline .
2. Now Connect your Wireless/router wire to PC which will not be direct from modem to PC this time and try to see if you get any signal make sure all adopters for wireless and modems are plugged in too .

It happens to me when i have to move from one place to another due to jobs and then after a while moving wires here and there within pc/router/wireless..modems works perfect.

Reset it to factory state.. there should be a small pinhole or Reset button for that.. press till countdown from 15 to 0.

And use it again..

Follow this steps will be helpful to any electronics
1)Just remove the power from modem and router for some time 5 mins and put it back to see if they work.Here you can try reset button on side/back of router as posted by some users with some pointed device that reaches there.
2)Try if you can use internet directly from modem without router first
if you can't connect call your provider
3)If you can modem is ok and work on router follow the manual if you are not sure
4)See wireless button are turn on/off
5)Search in google if you don't have manual handy or for any specific problem u face u will get at least 100 answers how to do that
Hope that helps.