We have an old .NET 3.5 web-site that uses RadEditor for rich text editing operations. The last version of the Telerik DLLs was 2011.2.915.35 and with this configuration, the web-site functioned well until end of December.
Currently, the RadEditor is blocked when you try to open it and
no text is rendered in edit mode. This is happening in all modern browsers
including Edge except in IE11 where it works only in compatibility mode. I
added the meta tag http-equiv="X-UA-Compatible" content="IE=EmulateIE7"
/> and it only affects IE11.
I upgraded to a newer version 2014.1.403.35 also downloaded the latest trial build 2018.3.910.35 with no luck - the same behaviour.