a) The referenced site tries to download and install some executable with something that pretends to be a browser plug-in;
b) A quick skimming of the Appeon start page made me think that Appeon is something that makes it possible to use PowerBuilder UI (and logic?) from web browser.
The above two points make me think that the browser does not display any html UI but instead just launches the mentioned plug-in and plug-in renders the UI in some manner (either via regular OS UI controls, or, more probably, by drawing them directly on its canvas or some other way).
You may try to use MSAA in TestComplete (like it is recommended for PowerBuilder, for example) and check if it helps.
Alternatively, you may contact Appeon's support and ask their recommendations as for how to access rendered controls using test automation tool (TestComplete).
Regards, /Alex [Community Hero] ____ [Community Heroes] are not employed by SmartBear Software but are just volunteers who have some experience with the tools by SmartBear Software and a desire to help others. Posts made by [Community Heroes] may differ from the official policies of SmartBear Software and should be treated as the own private opinion of their authors and under no circumstances as an official answer from SmartBear Software. The [Community Hero] signature is used with permission by SmartBear Software. https://community.smartbear.com/t5/custom/page/page-id/hall-of-fame ================================