How to Fix the Error
Solution 1: Remove any and all of the MacAfee programs from your PC.
One of the reasons for showing that “default gateway is not available” is the McAfee security program installed in the PC. Hence, to remove this problem go to the control panel of your PC, then enter programs and then go to program and features option.
From this option go to add or remove program option and select McAfee and then completely uninstall it.
After you uninstall this program, your issue will be resolved. To make your system virus free, you can install some other security product.
Solution 2: Reset the Wi-Fi or Ethernet adapter.
By disabling and then enabling the Wi-Fi from the network and Internet sharing menu, you can fix the issue.
The steps involved are as follows:
Right click on the network caption.
Then select “Open network Internet settings”. Then go to the option “change your network settings”.
Now choose from the menu change adapter settings by clicking on it. It will show your Ethernet connection adapter. Later you can choose it.
After selecting it, right click on it and opt the “disable” option. Wait for some time. Then select the “Enable” option and close the menu after it has been enabled.
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