An explicit value for the identity column in table can only be specified when a column list is used and IDENTITY_INSERT is ON SQL Server

SET IDENTITY_INSERT tableA ON

You have to make a column list for your INSERT statement:

INSERT Into tableA ([id], [c2], [c3], [c4], [c5] ) 
SELECT [id], [c2], [c3], [c4], [c5] FROM tableB

not like “INSERT Into tableA SELECT ……..”

SET IDENTITY_INSERT tableA OFF