For the time being, there are no reported issues with the unresponsive reconcile button in QuickBooks Online (QBO). I'll help you fix this to keep you going with your task.
When clicking a button or link doesn't result in any action, it indicates that pop-up windows are being blocked. Please note that troubleshooting steps may differ based on your browser and its version.
If you're using Google Chrome, follow these steps to check for pop-up blockers:
Open Chrome, select More⋮, then select Settings.
Under Privacy and security, select Site settings.
Select Pop-ups and redirects.
Choose the option to allow or disallow sites to send pop-ups or use redirects.
(Optional) If you prefer to keep pop-ups blocked, add an exception for QuickBooks Online instead:
Select Add next to Allowed to send pop-ups and use redirects.