iMIS 15 Installation Error

In order to see more descriptive errors you will need to disable Custom Errors:
In IIS Manager, right click the iMIS 15 virtual directory > Properties > ASP.NET > Edit Configuration > Custom Errors > Custom error mode > Off

Server Error in '/iMIS15' Application.

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Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 30: gWindowOnLoad = new Array(); Line 31: gPostBackFormProcessSubmit = true; Line 32: gUserLanguage = "<%= Request.UserLanguages[0] %>"; Line 33: gWebRoot = "<%= Asi.Web.Utilities.GetTildeExpansion() %>"; Line 34: gWebsiteKey = '<%= Session["WebsiteKey"] != null ? Session["WebsiteKey"].ToString() : "null" %>';

To resolve the above error:
IE > Tools > Internet Options > Languages > Add > English (United Staes) [en_US]

Refresh the page or restart the iMIS 15 client