I exported an IR from Powercab and compared it to a OH-IR.
The OH-IR is MONO 32 bit float / 48 kHz
The PC-IR is MONO 32 bit / 48 kHz
Looks like the Powecab do not accept float.
I was able to open and save the files without 'float' using WaveLab, and then use mp3tag to make sure all converted files had the correct 'title'.
Then they all did import without error to my Powecab.