Security Code image not showing

Hello,

When trying to book an appointment the Security Code image is not showing up.

Here is the response header:

Remote Address:205.153.119.7:80
Request URL:https://kellymobrien.com/?cpabc_app=captcha&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
Request Method:GET
Status Code:503 Service Unavailable
Request Headersview source
Accept:image/webp,*/*;q=0.8
Accept-Encoding:gzip,deflate,sdch
Accept-Language:en-US,en;q=0.8
Cache-Control:no-cache
Connection:keep-alive
Cookie:wordpress_test_cookie=WP+Cookie+check; wordpress_logged_in_b6e20c90fadd393f3abd5e27a253479a=joshuaiz%7C1400677837%7Ca7483030eb48d47c9a9f2b6b2ece0b53; wp-settings-1=libraryContent%3Dbrowse%26editor%3Dhtml%26imgsize%3Dfull%26urlbutton%3Dcustom%26ed_size%3D459; wp-settings-time-1=1400533777; PHPSESSID=qus68hqmckue877mm8jb2t6h74
DNT:1
Host:kellymobrien.com
Pragma:no-cache
Referer:https://kellymobrien.com/breakfast-of-champions/

How can I fix this? The security code is needed to continue.

Thanks!

https://www.ads-software.com/plugins/appointment-booking-calendar/