I don't understand why I can connect to internet using wifi on my iod, but not on my phone/3DS/ps4?

I have Mediacom for internet & bought my own modem/router (since I went through 4 of Mediacoms & was told buying my own would be better & more reliabl

I have Mediacom for internet & bought my own modem/router (since I went through 4 of Mediacom's & was told buying my own would be better & more reliable).
Last time, before I bought my own, when I called Mediacom for Internet issue & they came over all they did was look at the router (literally just picking the router up and looking at it) but refused to take a look at the computer to see what the problem could be.
I quote what the tech said to me when I asked for him to look at what it said on my computer.
"I see no problem with the router. We don't mess with computers."

My cellphone says it can't obtain an IP address & my ps4 says it can't obtain an IP address in the required time limit.
Hell, I even plugged my ps4 into my router with an Ethernet cord & it still won't connect to Internet.
I've done everything that the ps4's suggested actions instructed & still doesn't work.
I've talked to my cell phone provider to see if something is wrong with my phone & they said my phone is working just fine.

The only thing that I haven't tried is calling Geeksquad. But I'm hoping to find an answer here before paying someone to come over that may or may not be able to solve my problem.

or:I have Mediacom for internet & bought my own modem/router (since I went through 4 of Mediacom's & was told buying my own would be better & more reliable).Last time, before I bought my own, when I called Mediacom for Internet issue & they came over all they did was look at the router (literally just picking the router up and looking at it) but refused to take a look at the computer to see what the problem could be.I quote what the tech said to me when I asked for him to look at what it said on my computer. \"I see no problem with the router. We don't mess with computers.\"My cellphone says it can't obtain an IP address & my ps4 says it can't obtain an IP address in the required time limit. Hell, I even plugged my ps4 into my router with an Ethernet cord & it still won't connect to Internet. I've done everything that the ps4's suggested actions instructed & still doesn't work.I've talked to my cell phone provider to see if something is wrong with my phone & they said my phone is working just fine. The only thing that I haven't tried is calling Geeksquad. But I'm hoping to find an answer here before paying someone to come over that may or may not be able to solve my problem.

or:might need to upgrade internet

Tags:ps4,