As per checking on the updates in QuickBooks Online, the custom date range for the reports is not taken out. You may consider performing the browser-troubleshooting steps to check if this is a data-related issue.
Over time the data will become outdated and will cause odd behavior to any program you're going to access via browser. To start the process, use an incognito browser to check if you can see the custom data on the profit and loss page. If you can see that, go back to the regular browser and clear the cache. An alternative way is to use another supported browser.
Here's a screenshot of the Profit and Loss report that shows the Report period option:
I've added this article for future reference about tracking the specific aspects on your reports: Customize reports in QuickBooks Online. This will help you get the exact details you want to show in your report.
Please let me know if you have other questions. I'd be happy to help you further. Take care.