I had the same problem.
This fix might work:
$w.onReady(() => {
$w( “#dynamicDataset” ).onReady( () => {
let item = $w( “#dynamicDataset” ).getCurrentItem();
let url = item.EngMap;
$w( “#html4” ).src = url;
})
})
It worked for me.
If you still have trouble, check out this post (it helped me):
https://www.wix.com/corvid/forum/community-discussion/how-to-make-an-html-element-src-dynamic