In Winshuttle, when I get the SAP logon screen pop up the password field is grayed out and I cannot make changes.
Typically, you would expect to see this in environments where Single Sign on Policies or SNC have been implemented. You will want to consult with your Network/SAP team to verify these settings.
If you would like to disable the single sign on setting for a particular SAP system, you can :
1) Go to SAP GUI logon
2) Right click on the system, select properties
3) Select Network
4) Un-tick "Activate Secure Network Communication" as shown in the screen shot.
This will enable the users to put in a username and password when logging into the target SAP system.