Check these details and Square Sign In Login Page information here. If you are a first time user you will need to register your account or create a new one, otherwise you can login on Square Sign In Page with your previous login details.
These results are more helpful for you as these are anti checked and also verified by the system. You just need to open the Login page links nd enter your Login details like Login Id and Password and submit the information.
If you face any issue in your Square Sign In page Login, you can contact us from our Contact Us Page.