I have quite a lot of medium format film scanned as 16-bit TIFF files - those which were originally B&W images I converted to 16-bit greyscale in Photoshop in order to save a couple of hundred megabytes per image, as the 16-bit RGB TIFFs are around 300Mb each.
TP9 - current version, build 3946 - thumbnails these 16-bit greyscale TIFFs without any problem, but when I try to open any of them in the TP9 viewer, I just get a blank black window. If I convert one of them back to 16-bit RGB in Photoshop, then the TP9 viewer can show them without any problem.
The same 16-bit greyscale images display without any problem in Windows Photo Viewer, Photoshop, and Lightroom.
OS is Windows 8.1 x64, video card is nVidia Quadro K2200 with the current nVidia driver.