Unable to embed external link.

[doiphode]

When adding a url manually to a tab, we get this error
"Unable to embed external link. Your browser may be missing a required plugin or the link type might not be supported for embedding at this time."

we are using moodle v3.0.3 and used the current version of the block
https://github.com/oohoo/moodle-mod_tab/tree/MOODLE_30_STABLE