So when you cleared your cache, did you delete it physically from the browser settings or just attempt to do it via CTRL + F5? You need to physically delete the files in the settings. Have you queried the event logs on the database directly? Should help get a bit more info for you as well as looking into your local event log on your PC.
SELECT TOP 100 * FROM CMS_EventLog ORDER BY EventTime DESC
Kentico 5.5 R2 runs on Windows 10, if you have an old browser. I ran it about 2 weeks ago during an upgrade so there's no doubt Kentico 9 and 10 run on Windows 10.