I purchased a used Nitek Trio, and I have not been able to successfully change gases under water. I downloaded the manual from Dive Rite, and it says to press and hold the center mode button for 1-2 seconds, making the current mix flash, then press left select button until you get to your required gas and hold the mode button down again 1-2 secs. I tried that, and the whole display just flashed, and I could not do anything with it. Help!