If there are no global connections assigned then my fears are unfounded (except the "afraid of things I don't understand" one, because I don't understand why it didn't work and now does!
)
Quick spiel on the display types and remote connections:
An on top display is a display that opens over the top of another one. The previous display is still open behind it. Generally, these are used for popups. If you make them the full size of the screen, they will
appear to act just like replace displays, but all of your other displays are still open behind them. It's best practice not to use these for all you "full screen" displays because things like "previous display" buttons only work on replace type displays, and you may load the PVP processor up with updating all of the displays behind the one you can see continuously (don't quote me on that second one, I've not seen any official warning of such, but it would make sense to me).
A replace type display replaces the current display when it is called. This is what you should generally use for all your full screen displays. There are exceptions of course, but for the most part it applies.
In your global connections, you have two connections you can assign to do with the displays. Well, possibly more, but two that I'm interested in here.
Your "Replace Display Number" is
not, despite what you might well assume, a command to replace the display with display number
x, rather it is an indication of the
current replace-type display. You can use this to tell your PLC which display is currently showing on the PVP. Of course - this only works if you're using replace-type displays, which is another reason to use them where possible.
The "Remote Display Number" is a connection that you can assign which will command the PVP to select display
x. If you set this tag to 1, the PVP will display screen 1. If you set it to 7, it will display screen 7. This can be used to, for example, have your PLC bring up the alarms display when a new alarm occurs.
There are a few tricks to getting this working properly, and you must remember to set the Remote Display Number back to zero once you're done or the PVP will be stuck on that screen and unable to go anywhere else. But if you're not actually using that, not your problem - just something to keep in mind if you ever do.