Hi there,

As per your query, YES if you fail to submit your EWS category certificate your application won't be eligible for admission.

To change your category you can do it in the correction window which the organizing institute will open on 28th October to 13th November, with an extra fee.

Please check here all the information about GATE 2021: https://engineering.careers360.com/articles/gate-application-form-correction

Hope this helps..

Good Luck !!