Wi-Fi network could not be joined - Macbook Pro 2015 At first it said it couldn't find the IP address, I entered it manually and that got rid of the error message. 

Now it's just saying the wifi network could not be joined.

I've tried turning it off and on again, forgetting the network then adding it again. I've also tried clearing the PRAM and something else I'm not sure the name of (RMC or something similar). I'm now out of ideas.

Any suggestions?
I tried several of the suggestions posted online and none of them worked for any more than a few minutes. I’ve owned this MacBook Pro for nearly 4 years and never experienced this problem until a few days ago. So I asked myself what had I changed in the last few days. I realized that I had recently purchased a USB hub, so I did some searching and found out that you can’t plug the USB hub into the rear USB-C connection on the left side of a MacBook Pro - exactly where I had plugged mine in. So I switched it to one of the right side connections and bingo - everything works great. This solution worked instantly without making any setup or network modifications. Could this be your issue?