I thought this was being caused by recaptcha extension but is a smartmailer problem.
I am getting this error message
Notice: Array to string conversion in C:\HostingSpaces\TRICKSTAR\ericksenhonda.co.nz\wwwroot\ScriptLibrary\incSmartMailer.php on line 274

I have the latest version of the extension.

I think I've found the reason. It happens when I haven't put a redirection either in the smartmailer or the recaptcha.

Hello Phil,
We are going to check this issue.