Can you please try running these commands:
On Master:
Create Login [username] with password ‘password’
Create User [username]
Database Level:
Create User [username]
ALTER ROLE db_owner add member [username]
GRANT ADMINISTER DATABASE BULK OPERATIONS TO [username];
GRANT INSERT TO [username];
GRANT CONTROL TO [username];
Once done let us know the result. Also do check this document for more info regarding this.
Regards
Navtej S