If you have a table with an identity column, you can’t just do a simple insert. That identity column needs to be excluded from your insert statement.
There are times when you need to keep the ID values during your insert. Like moving data between environments.
Here is the SQL you need to allow your inserts to work.
First turn on identity_insert
SET IDENTITY_INSERT <TABLENAME> ON;
Then do your insert.
Then turn off identity_insert
SET IDENTITY_INSERT <TABLENAME> OFF;