A visitor fills in your form, sees "Thank you", and the message never reaches you. Or it lands in spam three days later. Most owners find out by accident, when a customer calls to ask why nobody replied. Every one of those is a customer who went elsewhere.

What I do:

With your go-ahead, check the form from the outside without sending anything: where it posts, whether that address answers, errors on the page, and your domain's mail setup (SPF, DKIM, DMARC). First findings within the hour.

With access, find the exact cause: form settings (Contact Form 7, Elementor, WPForms, Tilda), how the server sends mail, security plugins, captcha.

Fix it: sending through your own mailbox over SMTP, SPF, DKIM and DMARC records, the recipient address, and a clear message to the visitor if sending ever fails.

Send a test enquiry with you and show it arriving in the inbox, not in spam.

The full fix is from $100: I find the cause, set up sending through your mailbox over SMTP, add SPF, DKIM and DMARC, and send a test enquiry with you. Delivered in one working day from access.

Worked example on an invented company: the form was posting to a page that no longer existed and lost every enquiry. After the fix the enquiry is tested and arrives, and if sending ever fails the visitor sees the phone number. https://flowlab-dev.github.io/work/site-fix/

Send me the page with your form and within the hour I'll tell you what I can see from the outside.