Dear Ankur, GATE COAP is not an application portal. It is an admission portal. If you are an M.Tech applicant, you should register for GATE COAP on the basis of your GATE score after applying to the IITs of your choice. You shpuld register at coap.iitm.ac.in. 

Please go through this page for more information regarding the registration process: https://engineering-careers360-com.cdn.ampproject.org/v/s/engineering.careers360.com/articles/gate-coap/amp?amp_js_v=a2&amp_gsa=1&usqp=mq331AQCCAE%3D#referrer=https%3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s&ampshare=https%3A%2F%2Fengineering.careers360.com%2Farticles%2Fgate-coap

hello Ankur,

The (Common Offer Acceptance Portal) COAP-2019 registration link has not been activated. The registration process will begin from the 1st week of April (most probably from 2nd of April) after the activation of the COAP portal and will continue till 30th April. These are the tentative dates specified. Then the candidates with valid GATE scorecards can register.

For any more information, you can revert back here.

All the best!