Does the user has the privilege to export/import?

To export full database using data pump user must have EXP_FULL_DATABASE role or dba role and to import full database using data pump user must have IMP_FULL_DATABASE or dba role.
In order to see whether user has these privilege or not you can query,

SQL>SET lines 100 

COL privilege FOR a50 
SELECT grantee, granted_role, default_role 
FROM dba_role_privs 
WHERE granted_role IN ('DBA', 'EXP_FULL_DATABASE', 'IMP_FULL_DATABASE') 
ORDER BY 1,2;