SIMS-Sync will require you to have the SIMS External Connector in place.
If you are unsure what you need to do, please check the below links or contact your SCOMIS support team.
What is a SIMS External Connector? - http://faq.scomis.org/kb4249/
Creating the SIMS Account
When you create the SIMS Account as per the instructions (http://support.alfiecloud.com/solution/categories/126922/folders/208784/articles/136981-sims-configuration) please ensure that it created and present in the SIMS database.
If you create the account and can log on to the SIMS Terminal Server but cannot log on via the SIMS External Connector it is more than likely becuase the account has not been created correctly and therefore not present in the database.
For more information please contact your SCOMIS support team.