Canvas won’t re-upload my files -no file name changes! what now?

[jkr02230]

I posted an assignment, downloaded the student submissions and they became a zip file.  I unzipped it, graded each of the 18 submissions, re-zipped (with no change of file names) re-uploaded.  I got a page saying Canvas had posted each to appropriate student, however it did not recognize the following 18 submissions, so did nothing with them.  Of course that was all of them.  I then chose one student, wrote down her file name, and traced it.  No changes!  What is going on and what do I do now?  I am frantic!  I am so not-happy with Canvas right now.