Also, there were only specific UPS that the 5000 will work with. APC was listed as one of the brands, but through testing we discovered that only certain models.
To my knowledge Mitel no longer keeps a list of supported models (or at least that they would give to us).
You can verify that the 5000 see's the UPS by logging into the AWP webpage of the 5000, and browsing to the "System Information" section. There is a line for UPS, and it will either say "Detected" or "Not Detected".
There was also an event that got triggered when the UPS was plugged in, and would show in the logs. I don't remember specifically what that event was. But it was supposed to start a monitoring service.