No Pressure Data?

Pressure should be shown as soon as connected. 

Do you know what could cause it to sit at 0 psi on dry land? 

I apologize for the stupid question, no offence intended, but I have to ask anyway - is the valve open? 

Also did you follow the instructions shown in the following video? Some more details also at Getting Started With the Descent T2 Transmitter | Garmin Customer Support

Yes with the exception of I had the shop install a 6' hp hose in between (but I did adjust the part to the hp hose part). 

I also did the 270 degree turn and it worked but showed 0 PSI. The issue isn't that it doesn't show up as expected it's the PSI value is always 0 with the tank valve open etc. 

I had this same issue.  Brand new T2 descent would connect fine but would always read 0 psi with the tank on. We tried two different Mk2i computers and two different regulators.  We even put a T1 and an T2 on the same regulator.  The T1 would read the pressure.  The T2 only read 0 psi.  Tried to get some support from Garmin but didn't want to wait the 2 hours on the phone.  Since it was new, I just sent it back as defective.

I had this same issue.  Brand new T2 descent would connect fine but would always read 0 psi.  We tried two different Mk2i computers and two different regulators.  We even put a T1 and an T2 on the same regulator.  The T1 would read the tank pressure, and it could be seen on each computer.  The T2 only said 0 psi on each computer.  I even turned my wifi router off as I thought maybe there is some interference.  Nope.  0 psi was always the reading.  Tried to get some support from Garmin but didn't want to wait the 2 hours on the phone.  Since it was new, I just sent it back as defective.  Seems like poor QC.

I had same issue even after turning the T2 on from low power mode using the 270 loosening of battery cover. 
Support told me to remove the battery completely for 30 seconds and reinsert and that fixed the problem. 
Worth a try I guess. 

I have same problem.  My T2 worked fine for months and then stopped reading tank pressure.  I tried replacing the battery but it hasn't helped.  I contacted Garmin Support via the email option. I recieve the acknowledgement of email but no response yet after 4 days.  My 20 year old Scubapro transmitter is still working like a charm and has never missed a beat, I expected at least 5 years of trouble free operation from a high end product like this and I am pretty disappointed.  I had trouble with the T1 when I first got that as well, the battery would only last 6 or 7 dives and have to be replaced.