So even though this thread is old, I have pretty much the same problem.
I am trying to read an uncompressed Geotiff with 19 bands (float32) and get the same error:
OSError: cannot identify image file <_io.BufferedReader name='G:/Arbeit/Niedersachsen_LaubNadel/UNET/test/unet/data/sat/train/image/t_5120_3328.tiff'>
So far I realized that it is uncompressed and due to the filesize of 4 MB I expect it to not be a bigtiff. Any help would be appreciated.