Fuel Gauge stuck on half-full

I was involved in a collision and had my 2005 Prius (direct from Japan import) in a collision repair shop. The shop performed the necessary electronic checks and fixed the superficial damage to the Prius. After a time, the car was completed and I drove it off-the petrol gauge was at the half tank mark.

One week later, driving 80k (~50m) a day, my gas gauge is still at the half tank mark. I decided to fill up the tank. I paid for what seemed to be almost a full tank price...and the gas gauge increased by one increment only. It still hovers at one bar over the half mark.
Scouring the web, and this site, I found a fuel calibration protocol. Here it is:

1. Park the vehicle so as it is level,front to back and side to side.
2. IgOn (not Ready mode) and make sure that "Trip A" is showing on the odo (this is where we made a mistake).
3. Power down.
4. Keep your foot off the brake.
5. Push in and hold down the Odo/Trip button.
6. Push the Power button twice to IgOn (not Ready mode).
7. Turn the Odo/Trip off then On 3 times in 5 seconds (I pressed it three times within five seconds).
8. Continue holding the Odo/Trip button until a 6 digit code appears.
9. Release, then push again the Odo/Trip button for another 5 seconds. The 6 digit code will change to a 5 digit code.
10. After the middle digit,of the 5 digit code,changes to "1" release the Odo/Trip button and the odometer will return to normal reading

I tried this procedure several times. My problem is that at step 8 in this procedure, no 6 digit code appears. Does any one have any advice?