Digital boost gauge problem

[TheRedSlantnose]

I have two boost gauges on my 930 Slant; one analog and one digital. The analog one is a 934/935-style boost gauge made by VDO and measures in bar, and my digital one was made by AEM and measures in psi. The analog boost gauge works fine but my digital one doesn't. It still lights up and everything when I turn the key and occasionally flashes random numbers like 111, 222, 333 over and over while I'm driving, but somehow doesn't measure any boost. It was working when I bought my car, but at the time my turn signal relay wasn't installed, so I later brought it back to the dealer to have it installed, and that was when my digital boost gauge stopped measuring boost. I guess the dealer employees must've screwed it up somehow A friend of mine, who's also a Porsche enthusiast told me a vacuum line may've been disconnected from it, but I need some confirmation. Any idea what might be disconnected that I may possibly be able to reconnect myself?

Here's my VDO boost gauge (Sorry for the darkness, I took these photos with my car in the garage):


My digital boost gauge:


And the digital boost gauge on:



Thanks,