I can't add a new user to the system. The user, when logging in for the first time and filling out the form, receives the error: "The feature you've requested

Thanks for notifying us of the behavior you're experiencing when adding a new user in QuickBooks Online, @kadirov. 

As the error says, make sure that your browser has Javascript and cookies enabled. Also, there are times when a cache full of history and temporary files can cause unexpected behavior in the product. That said, I recommend opening your QuickBooks account through a private or incognito window. This is to rule out the possibility of a webpage issue, and private browsing doesn't store local files or cache.

If it works in incognito, you can return to your regular browser and clear the cache. This removes the history or log of sites so you can start with a clean slate. You can check this article to see the steps: Clear cache and cookies to fix issues when using QuickBooks Online. Otherwise, use another supported browser as an alternative.

If the issue remains even after performing these steps, it's best to contact our Phone Support team for further investigation. They are well-equipped with the necessary tools to look at your account through screen sharing. Here's how to contact them:
 

1. Sign in to your QuickBooks Online (QBO) company.
2. Go to the Help menu.
3. In QB Assistant, enter the topic you need help with. You can also enter questions.
4. Select Contact Us to connect with a live support agent.
5. Choose the Start a chat option.

Furthermore, you may refer to this article to see details on how you can manage users' permissions and how to delete them if needed: Add and manage users in QuickBooks Online.

Never hesitate to comment below if you have other questions about managing users in QuickBooks. I'll be around to answer them for you.