Issue with discount functionality and sub-total calculation while embedding app

Hi, I’m using Impact theme version 3.0.0.
While embedding the app to the site.

  • We were facing an issue in obtaining the discount functionality into the cart. For which I contacted to the support team, we did some backend coding to resolve it but still the Sub-total calculation is not working.
  • So, I re-contacted with support team and they informed the issue arises due to this currency converter app. Recommended with another app with supports “Amai Quantity Breaks and Gifts” Discount app.

This was the message received from the support team.

"We have checked and found that the problem with the wrong discount price is when you use the monetary conversion kit to another country (located on the left base of the Store menu), the product price will cause the discount wrong.

We see your shop has a currency converter. But our app always uses currency from Shopify settings to show on the store, because it doesn’t know what your currency is so it can’t change another currency. So they will be conflicted on the store. Therefore, the problem of incidents in the store is a problem from the currency conversion application you are using on the store. Please check again.
Therefore, please contact the theme developer or the developer of this currency converter app to check the cause of this issue on the store. The only suggestion here is to remove these 3rd party apps and remove their leftover code.
In addition, if you want to test the display of product currency prices in many countries around the world and not cause problems in the store, then you can install the Best Currency Converter app to test."

Can someone help me determine what the cause of this issue is and what the alternative solution might be to fix this.

https://apps.shopify.com/doubly-currency-converter?search_id=9136dedf-4490-4f2d-8e37-dc5c1f8b5186&surface_detail=best+currency+converter&surface_inter_position=1&surface_intra_position=1&surface_type=search