Not able to update version 3.6

Trying to update from Version 3.5.9 to version 3.6.

I select ‘update now’ and message then shows “Updated!”. When I refresh the page, the version is still showing 3.5.9 and message is displayed saying “There is a new version of YayMail – WooCommerce Email Customizer available. View version 3.6 details or update now.”