I had an issue installing on Windows and I scratched my head for about 30 minutes trying to figure out what it was. It turns out I extracted the .zip into my downloads and then copied that folder into the specified Mathematica folder. This caused me to have a nested folder, that looked like /MATLink/MATLink/ and this did not make MATLink happy. I would recommend tweaking the install instructions to warn against this.
I had an issue installing on Windows and I scratched my head for about 30 minutes trying to figure out what it was. It turns out I extracted the .zip into my downloads and then copied that folder into the specified Mathematica folder. This caused me to have a nested folder, that looked like /MATLink/MATLink/ and this did not make MATLink happy. I would recommend tweaking the install instructions to warn against this.