The error "User sign-ups are restricted due to technical limit violation." is caused by exceeding the total users limit depending on your QuickBlox plan.
You may check the limits on the pricing page.
In order to resolve the issue, please consider upgrading your plan to a higher one.
You can upgrade your plan in the QuickBlox Dashboard.
Feel free to check our official documentation for more information that will help you to integrate QuickBlox services into your applications / projects or contact our Support team by submitting a ticket if you have any other questions.