Hi,
In this case I suggest activating the default WordPress theme and recheck this issue, if everything went alright then it could be something related to our theme, but if it’s still not working then it’s definitely related to the form plugin you are using.
The safest way to do that is to install “Health Check” plugin and enable “Troubleshooting mode” as it can switch to the default WordPress theme and deactivate your plugins one by one. The good thing about “Heath Check” plugin is that it’s developed by WordPress team and it only affects your logged in session so that other visitors won’t be affected.
If you still can’t narrow down this issue, then please provide us with WordPress Dashboard login details in a “Secure Note” so we can investigate this issue.
Thanks.