When you suddenly can't connect to the Internet, do you know how to check the issue like this?
The First:
Unplugged or loose network cables are easy to miss yet one of the most common reasons you might suddenly find yourself unable to connect to the Internet. That's not a problem on wireless networks, but on most laptops the Wi-Fi radio can be inadvertently shut off instead. On home networks, it's also possible someone unplugged the router.
Please ensure your wired or wireless network hardware is switched on and plugged in.  
The Second:
Rule Out False Alarms
What may seem to be a network problem connecting to the Internet is sometimes simply a Web site (or whatever server is on the other end of the connection) being temporarily offline.
Please Before assuming your Internet connection is faulty, try visiting several popular Web sites rather than just one.
The Third:
Avoid IP Address Conflicts
If your computer and another on the network both have the same IP address, the conflict between them will prevent either from working properly online.
Please to resolve an IP conflict, follow these instructions to release and renew your IP address. If your network uses static IP addresses, manually change your IP to a different number.
Besides these three situations, the lack of wireless driver also can lead to the stop working of wireless. Here I provide you a way to do it:
Step 1.
Download OSpeedy Driver Updater for free and install it.
Step 2.
Connect your internet and activate OSpeedy Driver Updater.
Step 3.
The software could install wireless driver no matter what brand or what type automatically and perfectly.
Introduction of OSpeedy Driver Updater.
OSpeedy Driver Updater is dedicated to offering the best user-experience for you. With several clicks, you can download and install the most suitable driver for your computer or device. It can download and install drivers extremely fast,  get the right driver in several minutes.
In general, it takes users long time to scan and identify drivers. The special thing it can provide is that 24/7 customer service with professional technical team means you get help from our staff anytime you need it.
At the end of the article, I give you the last way:  If all else fails, contact your Internet provider to verify whether they are experiencing an outage. Some providers also give advice on troubleshooting problems connecting to their network (sometimes for a fee).
Thanks for your reading. Hope it helps.