I was able to connect my PC to wireless internet at my house without any problem....until a few days ago. There was wi fi connectivity problem with yellow symbol, means there is yellow symbol appear wifi bar. I try to solve this issue via Network Diagnostics and get the following error message: "Windows can't communicate with the device or resource (Primary DNS Server)."
Even my PC connected with full strength signal and I appear to be connected but there is "no internet access". This is really frustrating for me as the internet was working just a few days ago and I haven't installed/unstalled anything. After some CMD and pining I got the solution as below:

Step 1. ( For Router)

1. Connect to your router (by typing 192.168.0.1 or 192.168.1.1 in the address bar) and log in. Check your user manual or documentation if you do not know the log-in credentials.
2. Make sure you are in the Setup > Basic Setup category.
3. Scroll down until you see "DHCP Server" - if it is disabled, select "Enable".
4. Enable DHCP If you want, you can change the number that the DHCP IP assigning starts. (this is optional)
5. Use the DNS servers provided to you by your ISP. There are many DNS servers out there. It's best to use your ISP's if possible.
6. Scroll down and click "Save Settings".

Step 2. ( For PC )

1. Click on Start and then Control Panel.
2. Go to Networking and sharing center and then click on Change adapter settings.
3. Right click on Local Area Connection and choose properties.
4. Highlight Internet Protocol Version 6 and click on Properties.
5. Choose Obtain DNS server address automatically and press Ok.
6. Choose Obtain IP address automatically.
7. Repeat the steps for Internet Protocol version 4 as well.

Save new setting and restart tour Pc, Cheers ! you fixed this issue . Share your experience via comment.