It seems that there is something wrong with the code you are using. According to this thread: https://wordpress.org/support/topic/plugin-contact-form-7-text-field-length-change
You have to change your code to be something like :
[text* your-name 60×8]
It’s working on our demo without any of these. If this didn’t work, then please send me your admin credentials in a private reply and I will check it myself.