I have no idea if I'm supposed to do something aside from download a file and see what happens. Downloaded an EICAR test file (Google it. Basically, an industry standard harmless file with a specific string of gibberish for testing if AV engines work.) Downloaded several versions on the EICAR site. Normally an AV engine gets triggered if you do so.
First give the extension a try to make sure it works on your desktop computer. Note that it might tke up to 1 minute for the extension to scan the file. This is the limitation of VirusTotal. If it worked, then open a bug for Android version.