I have a transaction which is 'unreconciled in register', the system has an option to Reconcile the transaction again but when I click 'Save' it doesn't save?

I can help you save the Reconcile status in the register, info1685.

First, I'd like to ask if you've got an error when clicking the Save button. This helps me share appropriate information about your concern. 

While I'm waiting for your response, we can verify if the browser is causing QuickBooks not to save the status. Let's follow the recommendation below to resolve this unexpected behavior.

1. Refresh your browser by clicking the Reload icon or pressing F5 on your keyboard.
2. If it persists, log in to your account through an incognito window. 

• For Google Chrome browser: Ctrl + Shift + N
• For Mozilla Firefox browser: Ctrl + Shift + P
• For Safari browser: Command + Shift + N

Go back to the register and select R. Then, Save. If it works fine, we can clear the cache of your regular browser: Clear cache and cookies to fix issues when using QuickBooks Online. This will refresh your browser's settings. 

Aside from that, we can use other compatible browsers in QuickBooks Online. 

• Google Chrome: Version 78 or newer
• Mozilla Firefox: Version 76 or newer. 
• Microsoft Edge: version 75 or newer
• Safari: version 12 or newer (Mac only)

For guides and tips, we can check these article:

• Reconcile an account in QuickBooks Online
• Enter an adjusting entry for a reconciliation.

Also, we can run the Reconciliation Report to review the beginning and ending balances. Also, we'll see which transactions were cleared and left uncleared when you reconciled. Let's visit this article for more details: How do I view, print, or export a reconciliation report?

Know that you can tap me on my shoulder if you ever need anything else with reconciling your accounts in QuickBooks Online. I'll be around to back you up. Stay safe!