I recently installed iTerm on my new Macbook and eversince I had the problem that the pipe symbol was not recognized. The pipe symbol on a Mac is typed using Option+7 (which is simply ALT+7). In iTerm this was without any function.
The reason: iTerm uses Option+Number to switch between split windows (if you use any). The settings can be found in the general preferences, not in the individual profile:
If you see any Option usage in this setting just disable it and the pipe and all other characters with Option+Number will work again.