If your employees treat you as if you are invisible, there are a number of steps to help them see the light. The first is to look at yourself. If you have allowed them to treat you as background noise for some time, you have essentially condoned this behavior, as your employees have no reason to assume that you are unhappy with it.
Your employees might also be overlooking you because they are busy and believe you are not bothered if they continue to work when you enter. However, they might be ignoring you out a lack of respect. They may question your managerial ability, and if they have been able to snub you in the past and suffer no reprisals for doing so, they continue to play this card. They may sense that you will go away if they ignore you, especially if this is what you have done in the past.
If you do not like what is happening here, you should sit down with these employees individually and clarify what you expect of them when you walk into their offices. They do not have to stop doing business, but they do have to stop this business of ignoring you.
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