From the Release Notes included with the update: 

New in PR2.21.0.0
Employee records are no longer dropped during Payroll conversion from legacy to new Payroll
on Premium when in legacy employees are assigned a Benefit Code with Annual Limit of
99,999.00.
1
DevID 111005 Knowledgebase ID 99553
When reversing a payroll check using the Reverse Check button in Payroll Data Entry, the
default check date populated is the date of the original check but you can now manually change
the check date.
2
DevID 112333 Knowledgebase ID 106526
Error: "Error 15 SY_Maint.pvc 455" no longer occurs in Employee Maintenance when the Time
Off Annual Limit is 99,999.00.
3
DevID 112383 Knowledgebase ID 106893
Only the employee records populate the ACH file when Include Only Employee Records option
is selected in Direct Deposit Maintenance.
4
DevID 112451 Knowledgebase ID 107296
"The amount does not equal the rate multiplied by the hours" will no longer display on Payroll
Data Entry Audit Report for Salaried employees that are rounded.
5
DevID 112461 Knowledgebase ID 107352
Payroll Check History Report now retains the earnings/deduction code selections when saving a
report setting.
6
DevID 112467 Knowledgebase ID 107351
In order to calculate the Ohio Courtesy taxes a negative percent can now be entered in the
Override % column on the Taxes tab in Employee Maintenance.
7
DevID 112470 Knowledgebase ID 103721
Accrual Percentage field is now enabled on the Payroll Expense and Tax Accrual screen during
Payroll Check Register Update when the accrual date is changed.
8
DevID 112473 Knowledgebase ID 99805
1
The new Offer of Coverage Codes and the new Health Coverage Code for Individual Coverage
Health Reimbursement Arrangement (HRA) have been added for Affordable Care Act (ACA)
reporting.
9
DevID 112565

Sharlene, If you upgraded from 5.40 (2017) or earlier, we have upgraded our Crystal Reports Software and older custom reports (such as having a MICR code added) will have to be re-created. I hope this answers your question.

Thanks William.  This is just a 2.20.3.0 payroll update to 2.21.0.  Appreciate your reply.

Appreciate your reply but do not see an ID above that refers to changes in the check format.

I just had the same experience as Sharlene - client is on v2019.  PR 2.20.0 to 2.21.  Why is this happening and where is it documented?  Upon further review, it also replaced PR_Check1.rpt.  What was changed in these updated forms?

I have a client on 2019.4 - just updated from PR 2.20.0 to 2.21.0.  When printing Direct Deposit stubs, they are prompted the form needs conversion.  When they select Yes to convert, they get the message that the form is not found or does not exist.  Load report failed. I get the same message while logged onto the server with admin rights.  I did a Verify DB on the form (which is in MAS_System, as the client has over 30 companies).  The form changed.  After still receiving the message, I manually updated the Summary information to change the verbiage to "Converted to version P/R 2.21".  The form now prints, but I'd appreciate Sage reporting what the form changes are that require a conversion (and why it fails)..

This is a customized form.  Sage KB 55002 suggests restoring from backup, but that doesn't seem to make sense in this case (or copying the form from the main Reports folder.