Be sure that your browser is a supported one and configured properly.
Check this:
Recommended Browsers for Oracle E-Business Suite Release 12 (Doc ID 389422.1)
Also these, one of them may be exactly your case:
Some Users Get: Oracle error 1403 ORA-01403 ORA-06512 FND_SESSION_MANAGEMENT.CHECK_SESSION (Doc ID 1438938.1)
Login: ORA-01403: No Data Found ORA-06512: at line 1 has been detected in FND_SESSION_MANAGEMENT.CHECK_SESSION (Doc ID 1397575.1)
Note 1336030.1 - Login Page Throws Error 1403: Java.Sql.Sqlexception: Ora-01403: No Data Found Ora-06512: At Line 1