Inconspicuous errors in Acrobat are inherently difficult to diagnose. They most commonly result from either of Permissions or 3rd party software.
So I would try and find out if it is one of the two before I randomly press buttons on cleaning tools.
1. Is CEO admin of his own machine? If yes check profile permissions by setting up a new admin account on the PC and log in using these credentials to see if you can replicate the issue. If a new admin account has the same issue it is not permission based. If not check what the difference is between the admin and his account.
2. It could be Internet Security (IS) interfering. Adobe has a habit to make call for updates when it starts but also ever so often. The simplest thing is to disable Automatic Updates in Edit>Preferences>Update.
This is how I would start, try this and report back.
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