My 1099that was uploaded, TurboTax is showing the incorrect gain than the amount reported on the form.

You may need to delete this form and enter it manually.  What kind of 1099 form was this for (1099-INT, 1099-B, etc.)?

 

Have you tried clearing your cache and cookies first?

 

A full or corrupted cache can cause problems in TurboTax, so sometimes you need to clear your cache (that is, remove these temporary files).

 

Here are the official instructions for the most popular browsers:

• Google Chrome
• Mozilla Firefox
• Microsoft Edge

Each browser has a slightly different method for deleting cookies. Choose the browser you're using:

• Microsoft Edge
• Mozilla Firefox
• Google Chrome
• Safari

 

TurboTax FAQ: How to clear your cache 

TurboTax FAQ: How do I delete cookies?

TurboTax calculates gain from proceeds minus cost.

 your 1099 does not show a gain other than allowing you to do this arithmetic

what do you think the gain should be other than proceeds minus gain?