Weird but already had this problem with only one of our users. It disappeared after we made him full_admin temporarily...
Meaning : create a new security rule for that particular user, with * resources on every potential actions. Then, try to add data, if it works delete the security rule and try again.
I Have experienced this problem a few days ago. This problem only occurs in IE. Using Chrome solved the problem for me.
Qlik is aware of this problem and it will be solved in the next release ..
The problem is related to a bug:
- QLIK-76520 where in Internet Explorer you can not load the Data Connections
I hope this is does the trick for you too.
Kind regards, Tamarah