SmartCrawl is returning a blank page on sitemap

I’m having issues creating the sitemap with SmartCrawl. If all the plugins are active on the site, mydomain.com/sitemap.xml returns:

500 Internal Server Error

nginx/1.6.2

If leaving only SmartCrawl and the WPMU DEV Dashboard active on it, the sitemap returns a blank page and there is an error on the console log, but on the sources section the sitemap is available.

I noticed that the issue seems to be related to SmartCrawl not processing properly the sitemap. For rome reason it is created it on http instead of https. If typing https://mydomain.com/sitemap.xml directly on the browser, the sitemap is properly displayed, but the sitemap button under SmartCrawl > Sitemap page is pointing to http://mydomain.com/sitemap.xml, which returns the error.