Thank you for reaching out.
I understand that the product description is not loading properly and you've already removed the app that may have caused the issue. It is possible that some of the theme's originally coding was affected or accidentally removed. If you remember which files that the app had you modify, you can try rolling back to an older version of your theme for that particular file. Alternatively, you can also install a fresh copy of your theme to see if the issue persists - this can help determine whether it was caused by the app's coding or something else.
If you're unable to restore the product descriptions, our Theme Support team can assist you with this if you're using a Shopify-supported theme. While we’re not able to provide account-specific support via the Shopify Community at this time, we’d be happy to continue assisting you through live chat, email, or callback. Please visit the Shopify Help Center and log in to your account to create a support request. However, if you're using a third-party or custom theme, then I'd recommend reaching out to the theme developers for assistance with restoring your theme's coding.
Did the app require you to manually paste snippets of code into your theme?