Profit and Loss by Class has a "Not Specified" Class with a zero balance in it.

Greetings, @498399.

There's a possibility that the set up of columns and rows is changed. I'd be glad to help you to back your Profit and Loss up and running. 

Here's how:

1. Go to the Reports tab located on the left side.
2. Type Profit and Loss by Class in the search box, then enter.
3. Click Show non-zero or active only drop-down arrow, then select Active both rows and columns. 
4. Hit Run Report.

I've attached a screenshot for your reference: 

For additional guidance about customizing,  please check out this article: Customize report. 

To learn more about exporting, you may use this article for your future reference: Export your reports to Excel from QuickBooks Online.

Leave a comment below if you have follow up questions in your account. I'm always here to help. Take good care always!