I assume the "psc" in the title is a typo, and you're actually referring to a DSC PC1832 Control Panel for your alarm system.
As for your communication error---I'm sorry to be the bearer of sad tidings, but your system (and basically all contemporary alarm systems) just don't work well with VoIP phone landlines. The "fidelity" of VoIP is sufficient for voice transmission, but the signals transmitted between alarm control panels and Central Station (monitoring) Receivers is more demanding. Sometimes VoIP will work, more often it won't. Even when it does seem to work, we techs don't trust it to work every time. It turns out that the old POTS (Plain Old Telephone Service, i.e., originally known as the Post Office Telephone Service or Post Office Telephone System) line carries signals with greater fidelity. Unfortunately, for various reasons aside from cost, POTS seems to be getting close to becoming obsolete and unavailable.
Probably your best bet is to ask your monitoring company about alternate signal options, e.g., cell or internet, instead of landline.