It probably relates to security issues.

In the Office folder you will find selfcert.exe which will enable you to create a certificate for your own macros.

Having done that, set the macro security in Outlook to provide warnings for all macros, then start the VBA editor and from Tools > Digital Signatures, add your newly created signature to the project.

Close Outlook saving the project at the warning.

Re-open Outlook and you will get a security prompt for the vbaproject. From that dialog choose the option to trust items from the publisher (your certificate).

Thereafter the macros should work normally without prompts.