Useradmin blank on publisher

[Sutty100]

I am trying to access the user admin page on our publishers, unfortunately it is returning a blank page in some of our environments. The author page always loads. I need to make changes to just the publisher and also I want to check changes activated on the author are replicating down as it doesn't seem to be the case. 

What would cause the page not to display url I am using is: server:port/useradmin also tried sticking a .html on the end but no luck. Nothing obvious showing up in the logs either. Any advice would be great.

[Sutty100 · Accepted solution]

Worked out that the Apache Sling GET Servlet had JSON turned off on the publishers which is good for security I believe. Turned it on hit the link, it loaded, made changes then turned off json again. Its turned on and off via apache felix in the config tab.