Hi Kiran,
Hope you would not get offended but really wanted to understand that if i had purchased the paid package and service then your theme should work with each and every plugin. Earlier it was working but due some circumstances we have to re-stall the theme and post that it has stopped working.
Our entire website SEO gone worst due to the fact that your theme does not work with Yoast SEO plugin and now you wanted the FTP detail.
Can you pls. let us know the changes you wanted to make so that we can also take a look of the code and changes. Hence, in future if such issue come then we will handle the same by ourself.
We are planning to integrate with 3-6 website of ours.
hence, pls. suggest the way to work with Yoast SEO pluging.