SI CAPTCHA was developed for WordPress. WordPress MU is a bit different.
To use SI CAPTCHA on WordPress MU, it can only be installed in the plugins folder. I have not coded SI CAPTCHA to work from the mu-plugins folder. Which folder do you have it installed in?
also try setting to the default theme to test. Let me know how it goes.
= 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.
Your theme must have a <?php do_action('comment_form', $post->ID); ?> tag inside your comments.php form. Most themes do.
The best place to locate the tag is before the comment textarea, you may want to move it if it is below the comment textarea.
This tag is exactly where the captcha image and captcha code entry will display on the form, so
move the line to before the comment textarea, uncheck the 'Comment Form Rearrange' box on the 'Captcha options' page,
and the problem should be fixed.
= Troubleshooting if the CAPTCHA image itself is not being shown: =
This can happen if a server has too low a default permission level on new folders.
Check and make sure the permission on all the captcha-secureimage folders are set to permission: 755
all these folders need to be 755:
- si-captcha-for-wordpress
- captcha-secureimage
- audio
- gdfonts
- images