First, make sure that the file format is supported by TransMagic.
Sometimes, files are top-level assembly files that are missing their subordinate part files. To determine which part files are missing, in TransMagic, go to File->Settings, click the General Tab, and check the "Translation Log" option, click OK.
Then, re-read the file and TransMagic will display the translation log after the translation (or attempted translation). Then scroll down in the log file and you'll notice several warnings, for example see below. This portion of the log lists all the missing part files that TransMagic cannot find. These part files need to be in the same directory as the assembly files in order for TransMagic to read the assemblies. This was the case with all of the files you submitted. They are all assembly files missing their part files. You can copy\paste the missing files from the log and ask your supplier for these files.