After the plugin is activated, you can configure it by selecting the
Captcha options tab on the
Admin Plugins page.
Check the setting for CAPTCHA on Register Form: - The check box for "Enable CAPTCHA on the register form" should be checked.
Troubleshooting if the CAPTCHA form fields and image is not being shown:
Do this as a test:
Activate the SI CAPTCHA plugin and temporarily change your theme to the "WordPress Default" theme.
Does the captcha image show now?
If it does then the theme you are using is the cause.
Did you try testing with the default theme?
Try that to rule out your theme being the cause. Let me know the result.
Check and make sure the permission on all the captcha-secureimage
folders are set to permission: 755
all these folders need to be 755....
Did this fix it?