First of all, instead of temporarily suspending user registrations you could go to the Admin -> Spam section and tick:
Enable moderation (approval) of users: add registration fields
All new users must be approved
That way users will be able to register but would go into a moderation queue. I think it is better to disable registrations.
Regarding the not working captchas, I will have to assume that you're using a default installation, which comes with reCaptcha. So in the same section tick all the Use captcha... checkboxes. Save the settings. After saving the settings, in the same section, locate the Use captcha module combobox. There is an options text next to it. Click it. This will bring you to the plugins section and open the recaptcha module options. Click on sign up.
You will have to register in reCaptcha. You will be asked for a Google account and the domain names you want to use the captchas on, which I guess it is wikifirst.net in your case. Continue the process and you'll see a link for your domain. Click it. This will display the public and the private key, which look like this: 6McLMPgSGAAAACutJ_dHk-mRfxhoKzaJnztJCchn. Copy and paste both keys in the corresponding fields of the reCaptcha plugin options.
Then logout or open a private session in the browser and try to post anonymously, or go to the feedback page, or try to reset your password or try to register. You should see the captcha there.