Why not simple embed script from Visme

You should put it in source not in rich editor. Use the {;} button in toolbar.

I have just reposted this concern here as I am seeing similar case and use of <iframe>.

A user of our forum site tried to embed a 360 street view with the following code, shows up on the rich text editor with no issues but does not appear on the post after submission:

<iframe src="https://www.google.com/maps/embed?pb=!1m0!4v1507725217680!6m8!1m7!1s0pDgVCL2f7fqIKQTKSyDAA!2m2!1d9.317219321713546!2d123.3039477515308!3f282.23!4f-3.9399999999999977!5f1.1924812503605782" width="600" height="450" frameborder="0" style="border:0" allowfullscreen></iframe>

Forum URL: Negros Chronicle Forum

Post with issue: Traffic Management Office Concerns

Please see the following snapshot. Notice the embedded street view appears on rich text editor and only the code shows up on submitted post.

As a workaround, for the meantime, I've told the user to just put a link to the 360 street view and just post snapshots as overview of the situation.

We have tried to put it on "source", didn't work. 

I'm sorry but wpForo Embeds doesn't support Google 360 street view. We'll take this under consideration and add it in future releases.