Not able to add amounts to budget resources

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Created a manual cost only budget version. This have only one task. Added 4 resources and provided the amounts. But, when clicking save, getting the error - 

You can't plan for the selected dates because existing accounting periods don't cover the plan duration. (PJO-2205152)
Contact your project application administrator for assistance in creating accounting periods that cover the entire duration of the plan

We have,

Common Accounting and Project Accounting Periods - Yes

Calendar Type - Accounting Calendar
Period Profile - Accounting Period

Accounting Calendar Period Frequency - 4/4/5

2021 periods are defined Jan-21 till Dec-21, Till AUG-21 is open.

I am not sure, what is the issue. We upgraded to 21C this weekend.