Magento 2 Admin Extension Button Not Showing Javascript

[gt38er]

We have Latest Mirasvit Advance Feeds extension installed on our Magento 2.2.2. site PHP 7.1 - all the features of the extension are loading fine apart from the + button in the category mapping section. It basically a button that opens up category lists.

We have tried this extension on same setup but on another server and its working perfectly. other server is also running with php 7.1

After several weeks we are unable to fix this issue on live site with the developer or server hosting company as to what can be causing this issue. The permission / ownerships all seems to be correct and installation and upgrade goes without any errors.

We really need this to show so we can map the categories with googles and create the feeds.

Can this be database / javascript / php / nignx / apache / related ?

As I said we have same backup on another server and upgraded the extension and its working fine.

The previous version of the extension loads the category mapping button but doesnt after we update or even remove and install from scratch the latest version.

[amitsamsukha]

it must be a JavaScript issue or some conflict between 3rd party extensions. 

can you try the following commands : 

rm -rf var/view_preprocessed/ var/cache/ var/page_cache/ generated/code/ pub/static/adminhtml

php bin/magento  setup:static-content:deploy -f

and check browser console output, is there any JS Errors and into the network tab, there should be

2 JS files 
dynamic/category.js OR dynamic/category.min.js 

dynamic/category/search.js OR dynamic/category/search.min.js 

And 1 HTML 
category_mapping.html

also, you must check this by removing JS Merging and static-content deploy again.