When an Iteration is moved to Accepted Status, it is not displayed in the Iteration filter drop down page.
When an iteration is moved to Accepted it is generally no longer a displayed option in dropdowns. In many cases if you actually type out the iterations name it will be shown so it can still be selected. It's just not automatically included in the dropdown.
This is to prevent accepted iterations from making the dropdowns difficult to use since there can be a large number of them. In the past they were automatically listed in the dropdowns, but due to customer feedback they were removed which is why the behavior is currently what it is.