When you say, "I keep getting fault.", I don't know if you mean Zone 2 (1) is constantly faulted, or (2) if it keeps faulting intermittently. They're different symptoms; and troubleshooting is different for each set of symptoms. Which is it?
If your Zone 2 loop wire is solid wire (as opposed to stranded), repeated handling at the screw terminals can sometimes create a wire break inside its insulation near the screw terminals, so the wire looks intact, but is intermittently touching/opening inside the wire insulation. I've seen that happen a few times over the years. Use your fingernail along each wire on Z2 at their terminals to check for integrity. If Zone 2 is a powered device (motion or glassbreak sensor, or smoke sensor), then there are 4 wires involved, loop and power (usually Terminals 4 & 5).
If you're sure that the two wires for Zone 2 loop (circuit) are connected properly at Terminals 10 & 11, then the most likely cause for faulting on the zone is that something on the loop itself is actually faulted/faulting. To confirm that the trouble is in the zone loop and not the V-20P, remove the Zone 2 loop wires from the Panel's Terminals 10 & 11 (T10 & T11) and install either (1) a 2K Ohm resistor, or (2) a wire jumper across those terminals. Usually, there is a 2K resistor on the Z2 loop (the default programming), but the Panel can be programmed not to look for that 2K resistor if the zone is not a fire zone.
With nothing but the 2K resistor OR a jumper across T10 & T11, Zone 2 should show Normal (not faulted). If you still get a fault, then you have a bad Vista-20P.
Assuming the Panel proves normal, troubleshoot the Z2 loop.
(1) What is on Zone 2!? I don't want to go though troubleshooting protocol for door(s) and window(s), and then have you tell me that Z2 covers a basement flood sensor, or smoke sensor(s), or half a dozen other devices that it could be. Each alarm system is, by its nature, a custom installation; and I need you to tell me what I can't see if I were there looking at the Panel and Zone List.
(2) Assuming there is a 2K resistor on the Z2 loop, where is it? The manual says to put the resistor, called an "End-of-Line Resistor" (EOLR) at the end of the zone loop, i.e., at the sensor farthest on the loop from the Control Panel. Fire Code dictates that that is where the EOLR must be installed on fire loops; but savvy installers will often install burglary loop EOLRs at the Panel's zone screw terminals---T10 & T11 in your case. If your EOLR is installed at the Panel, it greatly simplifies troubleshooting the Z2 loop.