hi,

see I have checked the mhtcet 2020 information brochure. there is no particular date mentioned about ews certificate of issuing to verify for mhtcet2020. however for non creamy layer category, candidates need to submit the certificate which is valid upto 31 march, 2020. so since there is no particular dates of ews certificates is not stated in official brochure, then the current ews certificate would fine to do the application process. however you may also contact helpdesk for more  clarification. follow the below link to know more details:

http://view.mahacet.org/mahacet/admin/news_document/UG_Brouchure_09_06_2019%20Final.pdf