The error may appear when there's an issue with the browser. This is the reason why the custom reports disappear.
The best thing that we can do is to perform some basic troubleshooting steps. This way, you can get back to your business.
First, use a private browser to access your account in QuickBooks. It is also known as InPrivate in Internet Explorer and Incognito mode in Google Chrome. This browser mode doesn't record the browsing activity on your local device. You can access this by pressing the following keys:
Press Ctrl + Shift + N (Google Chrome).
Ctrl + Shift + P (Firefox).
Control + Option + P (Safari).
If you're able to alter your preferences, then let's clear the cache in your web browser or try using a different supported browser. It could be a temporary issue with QuickBooks and the current browser that you use.
Additionally, here are some articles that will help you in managing your reports in QuickBooks Online (QBO):