The issue is with Responsive Pro and not CyberChimps Free (the theme) as you posted in that forum? If so I will move it in the correct forum. We have not yet been contacted by WPML. The issue is strange on the first glance as Responsive Free is WPML compatible.
We were contacted by WPML. I did read through the forum thread on WPML and do not think that the issue is with the theme. I can be easily checked by switching to one of the default themes.
I am surprised to see that there is an issue between WPML and Yoast WordPress SEO, one of the top popular plugins. I am running both plugins on a site of mine without problems. You site map seems to be working. https://www.mandylaw.ca/sitemap_index.xml