This is a bit of tricky one...
Thanks for the screen shot it largely confirms that the source of the issue is that the communication between the browser and the IDE through the iframe is being blocked. We have a known similar issue with Safari but unfortunately we are not able to replicate this issue with Chrome, Fire Fox, or Edge (on Windows 10 or OSX).
In older versions of internet explorer there was a setting that prohibit communication through the iframe (which would cause something similar to this). However I have not found analogous settings in the modern desktop version of Chrome, Fire Fox, or Edge. So assuming you are relatively up to date (and not using extremely heavy handed security plugins on all your browsers) that seems unlikely to be the cause.
What type of device are you accessing the website from? If possible do you have another device you could try to rule that out as a source of the issue?