Running the Wi-Fi Troubleshooting tool
Almost all macOS devices come with a built-in Wi-Fi Troubleshooting tool called Wireless Diagnostics.d You can use this tool to identify the exact reason why your MacBook is not connecting to Wi-Fi. To run this tool, follow the instructions given below.

Step 1:On your MacBook's keyboard, locate the Option button.
Step 2:Now, click the Wi-Fi icon in the status bar of your MacBook while holding down the Option button.
Step 3:From the drop-down menu, select the Open Wireless Diagnostics option.
Step 4:In the opened pop-up window, click on the Monitor my Wi-Fi Connection option and follow the on-screen instructions to fix the wireless connectivity issue.
How To Fix Macbook Not Connecting To Wifi?
How To Fix Macbook Not Connecting To Wifi?
Updating the macOS
Sometimes, an outdated OS may also restrict the MacBook from connecting to the Wi-Fi network. To check and update the OS, perform the simple instructions given below.

NOTE: If you have enabled the auto-update option on your MacBook, then the update process will be initiated automatically whenever an update is available. Otherwise, you need to perform the OS update manually.

Step 1:Open the System Preference window on your MacBook.
Step 2:Click the Software Update menu followed by the Update Now or Upgrade Now button.
How To Fix Macbook Not Connecting To Wifi?
Step 3:Now, in case an update is available, it will be initiated.