Technical Support receives questions every so often about Pro Tools i/o issues and/or limitations. After some research we’ve determined that:
A Pro Tools 9.x, 10.x, and 11.x installation (Native) is limited to 32 i/o Channels (maximum).
Avid only supports the i/o on a single interface/driver.
There are situations where PT users have over 32 channels of i/o available and Pro Tools will not launch until the inputs in excess of 32 are disabled.
i/o must be recognized by the system as being a single interface (aggregate devices in Macs “may” work, but this is not a supported method)
The following link will explain some differences between versions of Pro Tools: