Mojave 10.4.3 WiFi problems

You can try to remove the network interface in "System Preferences > Network", select the network that isn't working, then press the "-" button.

And then add it back again by pressing the "+" and selecting "Wi-Fi" and naming it "Wi-Fi".

I have the very same problem however it is not a WiFi problem at all as my WiFi was fine. Talked to 3 Apple support advisors before they connected me with a senior advisor. The problem was that when I upgraded to Mojave I somehow Encrypted the OS which can easily happen. Seems the Encrypted version affects BlueTooth, WiFi which interferes with internert access. The solution was to do a back-up in Time Machine, then totally wipe (erase) your hard drive then reinstall Mojave (no Encryption)---And when you get to the option to transfer files, skip it and let it load. Then test your WiFi internet then restore any files. Worked perfectly for me. Most of the 1st level support people do not know about this issue.