hi,
can you enter msinfo32 in command prompt on SBS and look the os name?
If you can not uninstall connector ,you can restore your client system by usb key.like the picture.
If you finish restore your client system , you will need to check windows update and install update patch.
Create a Bootable USB Flash Drive in SBS 2011 Essentials
https://www.dell.com/support/article/cn/zh/cndhs1/sln283201/windows-server-how-to-restore-a-windows-small-business-server-2011-essentials-or-windows-server-2012-essentials-client-using-a-bootable-usb-flash-drive?lang=en
micorsoft security upadate against ransomware
https://learn.microsoft.com/en-us/security-updates/Securitybulletins/2017/ms17-010