Hello Ajay,
Below are the further possibilities.
If yet all the there was any XML format issue, please take the predefined payload(May be from Mapping) and transfer the data directly from SPROXY Transaction.
Go to SPROXY->Open your SI where you created the proxy->Click on Test button->Paste the payload and Execute(This test is just to test weather the actual proxy is triggering the proper payload or not).
Since you are using the proxy scenario on Java only Stack for the first time, you have check below configurations on ECC.
1. RFC Destination(G-Type) using SM59.
2. Integration Engine Configuration using SXMB_ADM.
3. Sender/Receiver ID using SXMSIF.
From PI:
1. Transport Protocol in SOAP Sender channel is HTTP.
2. Message Protocol is XI 3.0.
3. Within the module tab, you need to set the following parameters for XISOAPAdapterBean Module if you are using asynchronous commutation.
ignoreDuplicate= true and generateSysAck=true.
Please let me know accordingly.
Thanks
Venkat