Can I "unvoid" a check that was accidently voided after it was reconciled?

Hello there, @montrose-realest.

You'd want to view your audit log. This way, you can verify the details of the voided transactions and use it in re-entering the check transactions. I can guide you on how to do it.

1. Go to the Gear Icon.
2. Choose Audit Log.
3. Click the Filter button.
4. Select Reconciliations under Events. 
5. Click Apply.

Once viewed, you can now start re-entering the voided check transactions manually. After which, you can view the discrepancy report. The Total Discrepancy Difference on the report should be $0.00. 

Now, you can perform a mini reconciliation for the month of April. Here's how:

1. Go to the Accounting menu.
2. Select Reconcile.
3. From the Account drop-down, choose the account you're reconciling.
4. Since the Beginning balance is for February, you'll want to enter the Ending balance and Ending date as they're written on your bank statement for February.
5. Once done, click Start reconciling.

You can read through this article for more detailed steps: Reconcile an account in QuickBooks Online.

Also, I'd recommend consulting an accountant so you'd be guided accurately in reconciling your account.  

I'm happy to help some more if you have other questions and concerns about the reconciliation process in QuickBooks. Have a good one.