Hi

EWS certificate is valid only if it's signed by someone equal to or above the rank of tehsildar. Naib tehsildar is deputy tehsildar below the rank of tehsildar. Also according to JEE advanced official website

Candidates from OBC-NCL/GEN-EWS categories are required to have a valid category certificate in proper format issued on or after April 1, 2021, to be uploaded at the time of online reporting during JoSAA.

Hope this answers your query!