What happens when you open it in an incognito window ? Can you try restarting Kibana and provide the logs from that point. Also, If you open the browser debugger and watch the network tab when you load Kibana, what do you see? Are requests failing? If so, what's the URL they are trying to load, and what error does it produce? And also, are you seeing any error messages from the Kibana server (stdout or in log files)?
Also check to see similar posts : Kibana did not load properly in kibana version 6.6 may be the solution might work for u ?
Thanks
Rashmi