You need a valid license file?

Some xhr request is returning html instead of json.

I've seen this problem when multiple developers are working against the same database. Go into admin mode and check that the current page type is correct. It might be that someone has updated the page type and your local is different so just a rebuilt/restart of application might fix it.

Hi,

Thank you for replying GOSSO, Sebastian. But issue still persist at my end.

This error disapears after removing one rewrite rule(Converting URL to lowercase) from web.config.

<rule name="Convert to lower case" stopProcessing="true">
<match url=".*[A-Z].*" ignoreCase="false" />
<action type="Redirect" url="{ToLower:{R:0}}" redirectType="Permanent" />
</rule>

thank you.

A workaround, put a condition to your rule:

 <conditions logicalGrouping="MatchAll" >           
            <add input="{REQUEST_URI}" negate="true" pattern="^/episerver/$" ignoreCase="true"  />
          </conditions>

where /episerver/ is your cms root.

Good luck