Recordings come in too quiet

Hi everyone,
We are having some difficulties with our recordings coming in too quiet, using wavelab elements 7. We use a Yamaha M7CL mixer, which sends the performances to a Steinberg UR 22 mkII interface before it gets transfered to our computer. If We run a peak dB test using wavelab, the recordings come in at approx -5 dB on average. After all the editing is done, we use the function “Normalize Level” to boost the peak level to -0.5 dB, having stereo link check marked. If I compare our recording volumes to others, we are coming in way quieter.
I tried to use a software called “MP3 Gain” to boost our recordings. I could get them a lot louder, but I would like to find a way to do it right within wavelab. If I analyze our recorded tracks (with MP3 Gain) after I have all the editing and boosting to -0.5 dB done using wavelab, it states that these recording are at a Volume of approx 88-91 dB. If I load up other recordings and analyze them, they come in at approx -97 dB which is a lot louder.
Does anyone have an idea how we could get our recordings louder within wavelab?