If you see the error, it means cross-site tracking is enabled in your browser.
The Table Grid for Jira Cloud requires cross-site tracking to be disabled. The grid is rendering in an iframe and some browsers might treat it like cross-site tracking.
Disable cross-site tracking in your browser settings.
Jira displays only issue fields on the Create issue screen. The Table Grid for Jira Cloud is a table displayed on the issue view and edit screens, that is why it is not displaying on the Create issue screen.
You can pre-fill the grid with static data, or use edit issue screen to add data to your gird.
TGNG for Jira Cloud aims to display the actual grid values. Therefore values added in the configuration are considered as read only and are not indexed by Jira.
You need to update the grid from the issue view.
Navigate to edit grid from the issue view and save it. This helps to index grid default data.