I just tried a couple in both 20 and 21 and they dragged and dropped just fine.
Have you tried searching directly from within the object settings dialogue (rather than dragging from the website)?
Seems to be an issue with the portal doing it this way at the moment but it usually works.
Barry.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10