We have often had the same issue with pipes in profile view. The key is to extend the profile view well beyond the last structure - 100' or more. You'll be able to label the structure, or to see the label(s) you've already created.
C3D 2012, SP2
Dell Precision T3400, Windows 7 64-bit
Even though I had the alignment extended past the end of pipe/structure, I was not able to label it. I extended the alignment WAY past the end and yes, I was able to label the pipe. I also went back and just extended the profile view, it works. And doing some other testing, if I extend the profile view 34.07' more, the label works, if it's .01' less, the label will not show.
I'll get this problem sometimes if the profile view reads from right to left. Change the style to left to right reading, label the pipe, then switch back to right to left reading.
Is a portion of the pipe outside of the alignment station range? If so, Profile View Properties, Staions tab. Put in user values to make the profile view long enough to see the full pipe. You should also see the labels if this is the issue.
C3D 2012, RD 2012
Win 7 64, Core i7,
6 GB RAM, Quadro FX 1700
Civil3D 2012 (Service Pack 2.1)
Windows 7, 64 bit
Intel i7 2600 @ 3.40Ghz
16 GB RAM
Nvidia Quadro 600