Hello,

We have recently developed a simple add-in for Outlook developed in VSTO for
a number of our users, but with a few of the users, the add-in simply doesn't
load.

Currently, we have a setup package that installs the necessary keys in HKLM
and the necessary FullTrust code group in My_Computer_Zone. The add-in
creates a simple 2-button toolbar in Outlook. We tested the add-in on a
number of machines before pushing it, and it worked on all of them. After
pushing to approximately 30 users, however, we found that add-in toolbar did
not appear for several people (at least 4-5 that we are aware of).

Here’s where we are stuck: we attempted to fix the issue by installing the
add-in manually for each user. After installation, the add-in works as
expected under the Administrator account used for installation. If we log on
to a test account which has normal user permissions, the add-in also appears
as it should. However, when the computer’s main user attempts to load the
add-in, it still doesn’t load. We’ve tried completely uninstalling and
reinstalling to no avail. We’ve also tried logging to a file when the add-in
loads, but even this entry doesn’t show up, so it seems there must be some
setting/program on the user’s account which prevents the add-in from even
beginning the load process.

Our initial reaction was that VSTO or some other necessary dependencies
didn’t exist on the users’ computers, but the fact that the add-in works on
all accounts except for a single user has killed that theory. What could be
the cause of this?

Thanks,
Brian