I’ve just posted a reply to a forum post, including the URL of a 3Dwarehouse component set that I uploaded some time ago.
The correct image for the model containing the components appears in the post (as it does here), but clicking on it does nothing - I thought it should open a new tab or window on the warehouse at the correct page for the model.
I’ve included a text link as well by including the URL inside single backticks, which does work if you paste it in a browser, but it isn’t clickable here either.
https://3dwarehouse.sketchup.com/model/ef65bce7-6fbc-4d04-8de8-b4369e11afe6/Scaffolding-tube-couplers-Dynamic-Components
Has something been broken again? There was this thread (now closed) which seems to refer to the same issue, back in March 2017:
The issue hasn’t been solved at that time either. They created a ticket about it but problem was going on.
Maybe this time @rchanley and @Aerilius ? 
Hi all,
I just noticed that @Aerilius submitted a pull request to resolve an issue with the plugin related to Discourse security measures. It might take me a couple days to get to this, but I’ll test the changes out and get them through the process as soon as I can.
Thanks
And the 3D viewer is fixed again! Thanks @Aerilius!
(Side note: To get any old embeds to work, you may need to edit the original post that contained the 3DW link so the iframe is rebuilt. I’m not sure if there’s a way around that.)
I believe “rebaking” old posts (rake posts:rebake) should be able to generate the new onebox iframe. In the admin UI one should find it as “rebuild HTML”.