Recently we faced an issue that the cart in the home page is not working. Deactivated all the extensions and used base theme but still the issue was there. The issue was due to SMT. In SMT, for the botostarpa and all, we used external link. Due to the external link the cart was not working.
Below code was added int he SMT section.

So removed the unwanted links added for bootstrap .In SCA, we have default link for bootstrap and all. So no need to give any external link.
If any issues with the default working of SCA website do the following.
- Deactivate all the extensions and check whether the issue exist or not. If the issue still exist, then the issue is not due to extension.
- Activate the base theme and check whether the issue exist or not. If the issue still exist, then the issue is not due to theme.
- If the issue exist even after deactivating all the extension and used base theme, then the issue might be occurred due to SMT. For all the domains in the website, we are using same SMT. So check the SMT properly. If we are making any change in SMT it will effect all the domains in that website. So make changes carefully in SMT.