just purchased a new Dell Inspiron 15 with Windows 8.1. I have the laptop connected to my wifi network. The network signal is strong and all aspects of the connection work except, while using either Firefox or Internet Explorer, it will not stream Youtube videos above quality 144p. When I connect the laptop to LAN the videos stream just fine. Adobe Flash is up to date as well the network drivers and my Intel graphics card. Is there anything else I can do besides resorting to buying a new network card?

Are you facing issues only to play the YouTube videos?

This issue could be related to any related to any Wi-Fi connection or any YouTube settings.

Let’s try the following steps and check.
Method 1:
You may try running an Internet Speed test to check for the speed.

Method 2:
You may also get in touch with YouTube support and check the YouTube settings to see if the options for Playback to play High Quality videos are set correctly.
Method 3:
You may also try to “Turn off ActiveX filtering and Tracking Protection” in Internet Explorer 11 and check.

For further information, refer to the articles:

Use ActiveX controls

Use Tracking Protection in Internet Explorer