Hello,
Without access to your Dashboard, I can’t check your settings, so not sure where you selected center align.
Try t0 add the next code in Custom CSS for page area:
.wp-block-contact-form-7-contact-form-selector input,
.wp-block-contact-form-7-contact-form-selector textarea {
width: 100% !important;
}
.wp-block-contact-form-7-contact-form-selector {
text-align: center;
}
Regards