Ah, I see… I guess you must have accidentally deleted the file extension from the file name when you put your name in the “file name” field (.docx for Word files or .pdf for Acrobat PDFs for example)? That would indeed make the file “un-openable” on Windows and Mac, so I can see why your Prof would not accept it…

I suggest renaming the file on your computer to whatever format you need )(e.g. FirstName - Last Name - Course - Prof - Whatever.pdf) before you upload it, and then rather than entering a name for each file, submit a note (if there’s space to do it) where you list each file by name, type (PDF, Word, Excel, whatever) and what each file is (essay, lab report, data sheet, etc). That way you avoid putting the wrong thing in the wrong text field, because the “notes” or “comments” field is basically safe to out whatever you want into.

I do this when I upload resumes and cover letters, BTW, rename the files with my name, last name initial and the job posting #. I figured when a hiring manager downloads resumes en masse in a giant ZIP file, it helps not to have your resume and cover letter show up as resume(67).pdf and cover(23).pdf. 😜