In order to disable IPV6 in MAMP Pro, you need to disable IPv6 in Mac OS X.
1. Open Terminal and type the following command using the name of your network connection to disable IPv6.
Mac OS 10.7 - 10.11:
networksetup -setv6off Wi-Fi
Mac OS 10.10.3 - Current:
networksetup -setv6off “Wi-Fi”
2. Verify that IPv6 is disabled in Network Preferences. Go to System Preferences -> Network -> network connection Advanced -> TCP/IP and check IPv6 is set to Off.
Note: The old method of disabling IPV6 shows 'Off' in the IPV6 selection menu, however this is not included in later versions of Mac OS X since IPv6 will be used more over time.