MAIL2 attachment doesn’t work

Good morning,

I have a problem with sending automatic response with attachment (MAIL2).

Without the attachment the e-mail sends just fine, but when I add /uploads (from the wp-content folder) attachment file, then it stops sending. I do receive an e-mail on the fact someone has submitted their information, but then the autoresponder does not send.
I’ve checked so many different subjects on this (including: https://contactform7.com/setting-up-mail/ and https://contactform7.com/file-uploading-and-attachment/). So please don’t direct me to those websites :-), they didn’t help me out. The settings are correct, but the pdf is apparently not.

Size of file: 9 mb
Type: PDF
Location: https://flexibleorganisation.com/wp-content/uploads/2022/06/bouwenaaneenwendbareorganisatie.pdf (so i use: uploads/2022/06/bouwenaaneenwendbareorganisatie.pdf in the e-mail part)

Have tried to send it to Gmail and Hotmail.

Love to hear if anyone has the solution.

The page I need help with: [log in to see the link]