I know it´s an old question, but maybe this helps another person.
In my case the "on activate sheet triggers" didn´t work eather. I found out that the sheet-triggers can´t handle copy & paste values (in my case...).
I had to put a specific trigger (selection in field trigger) to multiple sheets and copied the field and the value, which was variable in notepad++. On every sheet where I needet the trigger i pasted the field and the variable, but it didn´t work there. Then i found out if you delete the pasted fieldname and write first
and then delete the = it work. It seems thant qlikview doenst recognice a field if you put it in the trigger with copy and paste, IF its an on activate sheet triggers. In other cases it did work well for me.....
Thanks Florian for the advice. Did your "On Activate Sheet Triggers" Not work work in AJAX and pluggin veriosn both? For us the triggers work in the pluggin version and does NOT work in AJAX mode. Were are using : Qlik 11.2 SR4