TIFF is common in scanning, printing and archiving because it can store uncompressed or losslessly compressed images, high bit depths, CMYK colour and several pages in one file. Web browsers mostly do not support it. Safari can display many TIFF files; Chrome, Edge and Firefox generally cannot.
This tool uses the browser to decode the file, so in browsers without TIFF support the file is marked as failed. On Windows, the built-in Photos app or Paint can open a TIFF and save it as JPG. On a Mac, Preview can export to JPEG.