HB is not recognising the .qfx file I'm importing

I'm setting things up from scratch and successfully imported a .qfx file from my bank account, but Home Bank won't recognise the .qfx file from my credit card company. I thought maybe it was because the account number in the .qfx file doesn't match what I entered as my account number, but I have no way of knowing since Homebank only says it doesn't recognise it... not why. I know the account number I entered is accurate, but online in that account it only shows as ...8844. I entered the full sixteen digits with spaces after every four (standard format for a Mastercard number), then I tried again by removing the spaces, and finally I tried by removing most of the number and listing it as ...8844. No matter, Homebank doesn't recognise this file, which has a .qfx extension.