Hello there, @pam96.
Thank you for posting in the Community. I'm here to make sure you get pointed in the right direction for support.
We currently have an open investigation for this specific issue. Our Engineering team is already working on a fix.
As of the moment, a workaround that I can provide is to refresh your browser when you're in the report page. Immediately select the Customize button, so you can access the customization tab.
I also suggest contacting our Technical Support team for further assistance. They can add you to the list of our affected users. This way, you'll receive a notification email as soon as an update is available. Open this article to see their operating hours, as well as the steps to contact them: QuickBooks Online Support.
As always, I'll be glad to provide further assistance if you need it. Enjoy the rest of your day!