The reason why users may be unable to create multiple accounts from the same computer or IP address is due to a protection layer that prevents hackers or bots from creating multiple accounts. It is also uncommon for a company to create multiple accounts for their company from the same computer. To add companies or employees, it is recommended to log in as an administrator or with permissions to do so and add them via the "companies" or "company contacts" options. Alternatively, employees can add their information from the main "create an account" page.
A customer is only allowed to create one account from the account creation page per IP address to protect your system against bots. The longer answer is in this video explanation
