Plug your butt set into the paging port on the ACS, you should hear the page. If not look at your programming. If yes, look at your paging amp input specs., it must be able to accept your paging output, if the amp does not accept what you are sending try a device to adapt it. On the IPO , I use a WMT1A, or something like that(number may be off but close) The UPAM comes with one in the box, Bogen makes it and Bogen has their own nameplate version of the UPAM, so you should be able to get it from them. Bogen product is one letter different I think in the part number. It is an isolation matching transformer if I remeber correctly.
You do not always get what you pay for, but you never get what you do not pay for.