When customers registration is enabled and customers try to make a booking using an email address already existing in your Bookeo Customers database, a warning message[1] will show and will be required to sign in.
They can click on the Sign in[2] button, then on the I forgot my password [3] link and follow the instructions to reset their password.
Your customers should not go to the Bookeo Sign in page for businesses to reset their password. They have an account with your business and not an account as a business. They will not be able to reset their password from the Bookeo Sign in page for businesses.