Lager carbonation woes

Hey all I need some help. I brewed a munich helles lager some time ago. The lagering period is done and I now have the beer on CO2 in a corny. I dont know why, but for the life of me, this beer will not carbonate. I have had it on 15psi for almost 2 weeks. I gave my brother the other five gallons and he is having the same problem.

Is it possible that it is somewhat carbonating but not producing a head due to the protein rest? I used pils malt for 75% of the grist and gave it a 20 min protein rest. I have never had that problem before though.

I don't know why both of our kegs would have issues carbonating if it was a hardware issue. We both have a red on our other line that has carbonated really well.

Any takers?

What is your force carbonation method?

I usually shake the the living hell outta mine at 30 psi for 5 minutes before leaving it on 15psi for a while (not more than 24hrs). Then lower to 7 or 8 psi for serving because all my tap hoses are pretty lengthy.

Nope, if your beer is on the pressure you say it is and the keg is sealed, your beer will carbonate. It's just forcing CO2 into solution, it's not like refermenting where you need to worry about yeast health/temp etc.

Either your keg is not sealed (there's a leak somewhere between the CO2 bottle and your keg) or your beer is not cold. Less CO2 will be soluble at room temps- there are charts and calculators. Most beers take about 2.5 volumes. Make sure you understand how to balance your draft system, so that your serving pressure is the same as your carbonation pressure, meaning at your serving temp, the correct # of volumes of CO2 are in your beer and you can serve on your lines without foaming. At my house, on my lines, in my fridge at my favorite temp and carbonation level, this is about 11 PSI @ 39F, with between 7 and 10 feet of line.

Wouldn't your serving pressure always be the same as your carbonation pressure at the same temp? I.e. I have my lager in my fridge at 40 deg. By the chart I use, I have set the lager to be about 3 volumes of CO2. The serving line is about 3.5 feet to the pearle taps I use. Anything I'm missing? Yesterday I relieved the pressure valve and CO2 came blasting out. I guess that part is the most confusing.

I guess I should clarify, my psi is about 15. Which is about 3 volumes at my temp