Not able to file itc-03

I have filed ITC-03 successfully with offline tool on 16th April 2018. But while making payment (offset liability) : "system error" message is coming. I am trying from last 4 days but same error message come. I have also raised greivance through GST Login Portal on 16th April but no reply yet and hence yesterday I have raised greivance through Help Desk also but getting no positive response. What should I do? Anybody else facing such problem ? What is late return penalty of ITC-03?