Use of Downtime Status when patching

I'm not sure if this is the correct forum, but I can't see an OAM forum......

The client would like a downtime window when we're applying patches.

I've looked around, and the only references I can find are:-

“How to use the DOWNTIME STATUS URL in OAM Schedule Dowtime [ID 376082.1]”

This states that is applies to Oracle Applications Manager - Version: 11.5.9 to 11.5.10

We're on 12.1.3, but thought I'd have a go at it as it's the only hit I can see, but it's not working.

I can access the downtime.html page directly by entering this URL, so I know the page itself is okay, but when logging on using the application completely by-passses the notification I've scheduled and so you don't get the message in downtime.html