I had the same issue, but as described in this thread it was also solved for me with version 5.1.1
However this issue seems to have reappeared with version 5.2.0 now.
Currently with 5.2.0 I get this behavior when “Implicit User Role” is disabled:
When not logged in, I just get a black page, no login page.
When logged in and I refresh the page, the Overview page just says “Loading…”. Also the item states in the Locations/Equipment etc. pages are not shown. The browser console then shows a lot of 401 (Unauthorized) messages.
When “Implicit User Role” is enabled OpenHAB works as expected.