tcastlecm

This worked for me. You can replace these values with your own.

}
.wpcf7 input[type=submit] {
background-color: #996633;
border: 2px solid #996633;
color: white;
font-style: italic;
font-weight: bold;
padding: 16px 32px;
margin: 4px 2px;
cursor: pointer;
border-radius: 4px;
}
.wpcf7 input[type=submit]:hover {
background-color: white;
color: #996633;
}

For me this turned out to be a webhost issue. They had moved us to a new server and DNS wasn’t updated on our LAN due to the move, which resulted in my attempts to fix the problem being made on the former website rather than the relocated version. Now that these have been sorted, everything works. Not a CF7 issue.
So if this happens to you, try to flush DNS.

For me this turned out to be a webhost issue. They had moved us to a new server and the MX entry was set to local instead of remote. This was exacerbated by a DNS issue on our LAN due to the move, which resulted in my attempts to fix the problem being made on the former website rather than the relocated version. Now that these have been sorted, everything works. Not a CF7 issue.
So if this happens to you, check MX with your host and flush DNS.

I have same issue
Please advise

Same here… we noticed a fall off in responses going back about a week

I have the same issue from mobile devices. When we send form via wifi it is delivered, on 4g mobile data it isn’t. Check email log with postman plugin and the latter never gets to the mail server. Also, when using mobile data, the recaptcha dialog does not show up. Tried removing recaptch from the form an still no go from mobile data, but wifi and wired lan work.
Please advise ASAP.