Hi Andy,

It sounds like you've done a lot of troubleshooting already, so let's see if we can get this resolved for you.

Firstly, it's great that you've looked into using Group Policy to configure the Trust Centre settings. This is definitely the best way to ensure that all users have the correct settings applied without having to rely on them manually configuring it themselves.

It's strange that the "Allow Trusted Locations on my network (not recommended)" setting isn't being applied even though you've enabled it in the GP. One thing to check is whether the GP is actually being applied to the users' machines. You can do this by running the "gpresult /r" command on the client machine to see if the GP is listed as being applied. If it's not, then you may need to check your GP settings to ensure that it's being applied correctly.

Assuming that the GP is being applied correctly, the next thing to check is whether the GP setting is actually being applied to Excel. You can do this by opening Excel and going to the Trust Centre settings to see if the "Allow Trusted Locations on my network (not recommended)" setting is enabled. If it's not, then it's possible that there's another GP setting that's overriding it.

One thing to note is that the GP setting for Excel may be different depending on the version of Office that you're using. For example, if you're using Office 2010, the GP setting for Excel would be located under

1. "User Configuration - Administrative Templates - Microsoft Excel 2010 - Security - Trust Center - Trusted Locations"

Make sure that you're using the correct GP setting for your version of Office.

If you've checked all of the above and the GP setting still isn't being applied, then it's possible that there's a bug or issue with the GP setting itself. In this case, you may need to contact Microsoft support for further assistance.

I hope this helps, and let me know if you have any further questions!