We've received reports from QBO users who are unable to save custom reports. Our product engineers are currently working to resolve this matter.
As a workaround, use an incognito or different browser to isolate the issue. If this works, go back to your regular browser and clear your cache. Sometimes a browser cache can be corrupted and can cause a variety of issues.
You can check this out on how to memorized reports. This link consists of steps that allow you to save the same settings of your customized reports for future use.
Also, I recommend contacting our Customer Support to add your company details on the notification list. This way, we'll be able to keep you updated once the resolution is available.
Leave a comment below if you have any other questions.