Includes of External Pages Not Working (PHP)

I have exec-php and runphp installed as plug-ins, but neither are working to show my includes.

For instance, my Concerts page is running php code very well. There are no includes.

My Calendar of Events page is trying to include https://www.mirdonamy.com/calendar.php inside of it. Mirdonamy.com is my root domain and ariellehaze.com is my subdomain. I want to be able to include pages of data from my mirdonamy.com databases. On mirdonamy.com the calendar.php page includes very well, no trouble at all. When I include that page inside a wordpress page, it makes my page look blank and disjointed.

Please advise!!

https://www.ads-software.com/extend/plugins/exec-php/