Managed to work this out.
I used Fiddler trace to see what was happening and saw the following error:
POST https//clarity-sandbox.business.com/reportservice...ces;includeInactiveInvestments,showGraphs/values 400 Bad request
So I did a bit of digging on this and discovered that it was down to an IIS setting.
The problem is because, the default character limit of each parameter in url is 260 which is defined in the registry.
So, you have to update the registry to increase this size limit where the IIS Server is running.
Registry location
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\HTTP\Parameters
Then you need to add the value name UrlSegmentMaxLength. If it is not there, create one with Type of REG_DWORD. And specify a higher value for value data such as 1000 in hexadecimal or 4096 in decimal.
Restart http on your app server using net stop http followed by net start http and the problem was resolved.