The input collection actually works fine for me but, as I said, it is very sensitive. Adding a single space in a card's name results in the program crashing. I intend to create a proper and more robust collection importer, but this is the current state of things.
You could try inputting a fraction of your collection, to test it out. If it fails it means a card's name was probably misspelled among those cards so it should be easier to pinpoint it. By inputting only small fractions of your collection at a time you will be able to confirm if the system actually works or if there is another problem. For me at least the input collection works but its extremely sensitive and fragile.