theApplication().ShowModalDialog functionality working on one environment but not on other

Hello,

We have DEV,SIT,AT and PROD env.

The issue is

theApplication().ShowModalDialog("msgbox.html", arr,"dialogHeight:150px; dialogLeft:200px; dialogWidth:500px; status:no;help:no;"); is working on DEV,SIT and PROD but not on AT, it is showing blank dialog box, not even showing .

Have checked with the script,it i similar across all the environments.

One more query if someone can provide me the information of first parameter of this Method ie.url, in my case it is "msgbox.html", where it is located , where can I find it.Any additional information will be helpful.