Code looks like it’s being generated by a Plugin (fbuilder?)
<div>
Please enter the security code:
<br>
<img id="captchaimg_3" border="0" alt="security code" src="/?cp_contactformtoemail_captcha=captcha&ps=_3&inAdmin=1&width=180&height=60&letter_count=5&min_size=25&max_size=35&noise=200&noiselength=4&bcolor=ffffff&border=000000&font=font-1.ttf">
<br>
Security Code (lowercase letters):
<br>
<div class="dfield">
<input id="hdcaptcha_cp_contactformtoemail_post_3" type="text" value="" name="hdcaptcha_cp_contactformtoemail_post" size="20">
<div id="hdcaptcha_error_3" class="cpefb_error message" style="display:none;position: absolute; left: 0px; top: 25px;" generated="true">Please enter a valid captcha code.</div>
</div>
<br>
</div>
If this works on other sites, I suggest you compare code on working sites with above. The <img> tag would be the first place to examine.
Maybe @nikeo will have an idea.
