Error while trying to send message on webpage

I have one main website and from that website, I have 4 sub-domains. So the main website is https://www.example.com and each sub-domain is https://www.example.com/sub-domain1, https://www.example.com/sub-domain2, etc. They all have their own WordPress logins. I have created contact forms in each domain/subdomain using Contact Form 7. All work properly, except on my main website. The formatting is exactly the same everywhere so I am confused as to why it is not working on the main website but have no problems on my 4 subdomains. Please help!