If you still haven’t solved your Wi-Fi worries you could use Apple Diagnostics to check for Wi-Fi or network issues.

To do so follow these steps:

Disconnect all external devices (except the keyboard and screen).
Shut down the Mac, then turn it on while pressing and holding D.
When you see the screen asking you to choose your language do so, then watch as the progress bar indicates that your Mac is being assessed. This takes 2-3 minutes.
If problems are identified, Apple Diagnostics will suggest solutions.