I can not set up a new user

Thanks for bringing your concern here in the Community about setting up a new user for your business, Anil.

I also recognize the efforts you put into the issue you've encountered. Let me go into details about this and provide some help.

Since you have encountered the same error while trying to set up a new account and have already attempted the troubleshooting steps, I'd suggest contacting our QuickBooks support team directly. They have the expertise and necessary tools to assist you further with required steps to enable setting up for a new user.

Here's how:

1. Log in to your QuickBooks Online (QBO) company.
2. Click the Help button at the top right corner.
3. Go to the search tab, then select Contact Us.
4. Enter a summary of your concern, then click Continue.
5. Choose a way to connect with us. You can either choose to chat with us or have us call you. 

Additionally,  I'm adding this article to have more tips and resources while working with QuickBooks in the future: Help articles, video tutorials, and more.

I'm only a few clicks away from assisting you with your queries. Please know that I'm looking forward to having you again here in the Community. Stay safe.