parse.com - Windows Phone 8.1 Parse

i have been trying log in parse using windows phone 8.1, have entered windows .net key & application id getting error:

"argumentexception unhandled user code exception of type 'system.argumentexception' occurred in mscorlib.ni.dll not handled in user code

additional information: header x-parse-os-version has empty value."

does have ideas why happening? code written

public app() { this.initializecomponent(); this.suspending += this.onsuspending; parseclient.initialize("applicationid", ".netid"); }

i had uninstall latest version (1.5.3) , install older version

install-package parse -version 1.5.2

still trying push work no success. sigh

WIKI