The configuration profile file(.mobileconfig file) might not download on the iOS mobile due to the file being invalid. While installing it on the phone by clicking on it, it will show "Error" or it will ask to open the  file using an application.

Unable to download mobile configuration file, for kerberos authentication on iOS device

All supported environments

The above issue can be seen if the mobile configuration file is not valid. It should be checked that the values of all the fields are correct and there are no formatting issues in this file. The formatting issues in the file can be checked using the following link.
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https://www.xmlvalidation.com/
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However, if a field value is incorrect or missing something in the file, it will still have issues downloading. One common issue that has been seen preventing the file download is described below.
- "http://" missing in the "URLPrefixMatches" section. It should be of the following format.
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<key>URLPrefixMatches</key>  
            <array>
                <string>http://spotfireServerURL</string>
            </array>
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