I have a deleted file archive database that stores the ID of the file that was deleted, I want the admin to be able to restore the file (as well as the same ID for linking
I believe it needs to be done in a single query batch. Basically, the GO statements are breaking your commands into multiple batches and that is causing the issue. Change it to this:
SET IDENTITY_INSERT tbl_content ON
/* GO */
...insert command...
SET IDENTITY_INSERT tbl_content OFF
GO