Sometimes the signs are small at first
A network problem does not always arrive as a major outage. Often, it starts as little things that slowly become part of the routine. Wi-Fi may be unreliable in one area. A printer may disconnect now and then. Calls may drop. Certain systems may feel slower than they should. Over time, those things can start to feel normal, even when they are signs that something underneath needs attention.
That does not mean anyone has done anything wrong. It usually just means the network has been in the background for so long that no one has had the time, support, or peace of mind to stop and really look at it.