Hi Varsha,
For me it works only at time, its totally weird 
.
May be you can restart the device and try or update the EPM to the latest or press that try again button (once it worked for me that way 
) . Check out the below URL, it explains about the different MOB errors you get.
http://help.sap.com/businessobject/product_guides/boexir4/en/410_mobiPad_errmsgs_en.pdf
I have raised a OSS message for an issue which i am facing in my BPC 10.1, may be their solution might fix this. Will update here if its fixed.
Regards,
Prithivi Raj