Don't use any of these characters: * ? < > | " : \ / (asterisk, question mark, left and right-angle bracket, pipe, straight quotation marks, colon, BACKSLASH, FORWARD SLASH). Also, don't add the .qdf extension; Quicken does that for you.
After adding accounts, see if you are experiencing the same problems in this test file.
If you don’t mind, could you please provide a screenshot of the error message you described receiving? If needed, please refer to this Community FAQ for instructions on how to attach a screenshot. Alternatively, you can also drag and drop screenshots to your response if you are not given the option to add attachments.
I look forward to your response.