Why is Quickbooks online sick pay accrual not working? It appears to have stopped accruing hours earlier this year for all employees.

I recognize your quick action regarding your sick pay accrual, which stopped adding hours earlier this year to all your employees, Greg. I also appreciate the gesture of specifying the QuickBooks product you utilize. 
 
The first thing you will need to check is your setup policy. Review the option you choose when scheduling the sick pay accruals. It will not accrue to your expected date if you select the incorrect one.

It is also worth noting to make sure that the sick pay policy you created is assigned to all of your employees to accrue the hours correctly in the right schedule you set.

You also need the Current balance because hours will not add if your employees achieve the maximum limit you set up.

With regard to correcting employees' missing accruals for months, you will need to manually calculate them to determine the number of hours that were not accrued. Then, you can add them to their current balance if applicable.

However with that matter, I will need you to contact your accountant to guide you on how to place it in QuickBooks without damaging your payroll records, as well as accruing it to your employee's sick pay hours accurately since we are dealing a prior months that has been processed.

Tracking employee accrual items correctly is essential, especially the sick pay option, since this affects their well-being, and some states do have correct calculations for this. Make sure to return here if you have additional questions about setting time off policies so we can assist you right away.