Hi,
Greetings.
I'm a Senior Oracle / Oracle APEX Consultant with 9 years experience & mentor team of OracleAPEXConsultant.
Oracle APEX uses native connectivity. Based on error code you'd mentioned I can say that it may occurs for # of reasons. To fix this we need to check logs and need to identify root cause. I've already fixed the same error # of times.
I am available to chat by IM, email or Skype, and would be happy to set up a convenient time to discuss the application.
Looking forward.
Thanks & Regards,
Jaydipsinh Raulji
Skype: jpraulji