New field inserting to Ax table not synchronizing when that particular table in sql replication.

  1. Replication configured with

a) Two publications ( AxTable with same name and same columns)

b) One subscriber.

The final output from the above configuration the subscriber must show the contents of two published table’s data in to one table.

  1. If any new column and data added to the published Ax tables.It is not synchronizing the table with new column and data. it is throwing the error below. any one tell me the solution please.

Object Server 02: The database reported (session 3 (Admin)): [Microsoft][SQL Native Client][SQL Server]Only members of the sysadmin fixed server role or
db_owner fixed database role can perform this operation. Contact an administrator with sufficient
permissions to perform this operation… The SQL statement was: "ALTER TABLE CUSTTABLE ADD FIELD1 NVARCHAR(10) NOT NULL DEFAULT ‘’ "

But the user, whose is logged in AX and trying to add a new field is having the full rights to SQL Server.
He is having sysadmin & db_owner rights.

What could be the problem?