Issue for Custom PO Approval application in Fiori

Hi Experts,

I had developed a simple Approval app but i am stuck with approval process, i am getting a following error message.

here is the code i did for approval button press..

I also tried with proxy, got this below error

I am very new to fiori so iam not getting where i am wrong is it a network connection issue or Data binding is not done properly in my codeing?? Because when i put break point in ABAP code nothing is getting triggerd.. please help me figure out this.

Please check the following ScreenShots

Any help will be appreciated.. Thanks in advance