Server Requirements

Supported web servers: 
Apache, LiteSpeed, Nginx, Lighttpd, IIS, WebServerX, uWSGI

php5.6x – tested up to – php7.1x max!
cURL support = enabled

allow_url_fopen = on
Recommended settings for your ->  php.ini file.
error_reporting = E_ALL|E_NOTICE|E_STRICT
display_errors = Off
log_errors = On
memory_limit = 256M
max_input_vars = 20000
max_execution_time = 300
max_input_time = 600
upload_max_filesize = 100M

And for using maps you may need to go ahead and add these to the php.ini file as well.
MYSQL 5.6  –  5.7 max
You MUST disable strict mode! – If you attempt to install and get an activation error then this may be the reason!
If you are on a vps or dedicated server then you will typically need to do this in 2 places = phpmyadmin as root under variables link (google it) and also in the etc/my.cnf  and then reboot mysql and it should be good to go.
(if you’re on a managed hosting then they typically already have “Stric” turned off as we do on our servers.)
Next you will possibly need to open up TCP ports if RETS connection fails and or you have any of these “Numbers” within your RETS connection url.
TCP –  6103  |  6160  |  8080
* example url: