You are currently making a booking as a TUI employee, but the name you entered is not recognised. Your name should be registered in order to be able to make a booking as an employee via the website. You can apply for registration of your name via the TUI Colleague Holiday Store.
If you don’t want to make a booking for yourself, you should continue as a TUI customer. If your name is spelled wrong, you should continue as an employee and correct your name.