Hello 5uwebsite,
Thank you for reaching out to our technical support forum. I’m sorry to hear about the trouble you’re experiencing.
Joomla has removed recaptcha plugin from Joomla 5. You can check Joomla 5 release note:
Joomla 5 Release News
They have mentioned here:
Enhanced Security: Events have been migrated to their classes, and the removal of no longer functional Recaptcha plugins boosts security.
You can use Invisible reCaptcha or try other recaptcha like hCaptcha. hCaptcha works fine with SP Page Builder. Here is the documentation link:
SP Page Builder hCaptcha Integration
Best regards