Whether you get an additional refund for the unemployment exclusion does not depend on whether you had tax withheld from your unemployment benefits. When you filed your tax return you paid tax on the unemployment benefits, even if you didn't have tax withheld. You will get an additional refund if you reported unemployment income on your tax return, the tax return that you filed did not already have the unemployment exclusion on Schedule 1 line 8, and your Adjusted Gross Income (AGI), not including unemployment, is less than $150,000.
See the following IRS announcements and FAQ for more information about the unemployment exclusion.
IRS to recalculate taxes on unemployment benefits; refunds to start in May
IRS begins correcting tax returns for unemployment compensation income exclusion
2020 Unemployment Compensation Exclusion FAQs