Hello @pvij
I understand how this is important for you, but in this case, you may consider contacting a developer to further assist you. But allow me to highlight some possible causes:
– Your website use a plugin to create a contact form and it’s not proprely configured/
– The provided said you don’t use their mail server, which means you use an external mail provider, in this case, it could be any provider From Gmail to SendGrid
– Mail server using the protocol SMPT uses the ports 25,465 and 587 and outgoing ports must be open, in case they are filtered, you’ll not be able to send the emails, the difference between the ports are the protocols they use SSL/TLS, etc
– Another possible cause, would be the fact the website was configured to use as an example SendGrid but the account was canceled/suspended or reached the limits per day.
– Could be also the fact the plugin is inactive or corrupted.
But since you are not familiar with the website or the tools, the best way to troubleshoot would be to contact a web developer or someone with experience with WordPress.