Occasionally things go wrong and need resetting and owners of Tesla's are familiar with the need to reset the computers. However even that can not cure all problems.
One such problem which can be often easily fixed by the owner is the window either not closing correctly or appears closed however the car reports the window is open and alerts the owner.
Car doors with frame-less windows like typically drop the window slightly when opening and then once the door is closed, the window closes itself. These windows are found on a number of Tesla models. It does this for a couple of reasons but the main reason is the window drop ensures the window is clear of the body work when opening, and secondly the contact it makes with the rubber seal is better if the window closes slightly when shut rather than simply closing onto the rubber seal.
If the car gets confused or loses track of the window position, then a couple of problems can occur. One is the window is left slightly open which can let in rain if not be a security issue. The other extreme is the window appears shut, but the car thinks it is open which can trigger a warning notification to the owner, and in extreme cases may even prevent the car alarm arming. The cure for both is the same.
The fix is really easy.
This is all you should need to do to reset the window. If the issue persists then you will need to raise the issue with Tesla.