COGS not calculating for all items

Glad to see you here, @beriksen12.

We can run the  Verify and Rebuild Data Utilities to get this sorted out. The Verify Data utility identifies any potential data damage issues. While the Rebuild Data utility repairs damaged data in your company file. 

Also, the cause why it's showing zero COGS on the income statement and Balance Sheet is the opening balance that doesn't have a price or purchases with zero amounts.

Before this process begins, please secure a backup copy of your company file.

Here’s how to verify:

1. Go to the File menu.
2. Select Utilities.
3. Click Verify Data then select OK to close all windows.

To rebuild:

1. Go to the File menu.
2. Select Utilities.
3. QuickBooks will ask to make a backup before rebuilding your company file, select OK.
4. Once the rebuild is done, click OK.

For additional information, you can check this article: Verify and Rebuild Data in QuickBooks Desktop. This provides an overview of how to check for the remaining data damage issue.

Also, once you fix the cost it will automatically update the COGS without changing the 2019 taxes.

In case you want to adjust your product’s quantity, value, or both, you go to this article and proceed to Step 3: Adjust your inventory quantity or value in QuickBooks Desktop.

You can always get back to me if you have any other questions. It'll be my pleasure to help you. Have a good day.