Will My Unfiled 2021 Tax Return (Potential $4.1k Refund) Delay My 2024 Refund Processing? IRS Confirms No Record of 2021 Filing

Need help understanding if my unfiled 2021 return will hold up my 2024 refund. Just found out about transcripts on the IRS website and realized I never filed 2021. I accessed my IRS transcript information and received a letter clearly stating: "Return: 1040 Information About the Request We Received On February 21, 2024, we received a request for verification of non-filing of a tax return. As of the date of this letter, we have no record of a processed tax return for the tax period listed above." The letter confirms what I feared - they have absolutely no record of my 2021 tax return being processed in their system. I got last year's return with no problem, but now I'm worried this unfiled 2021 return will cause issues with my upcoming refund. The letter even includes the IRS contact number: "If you have any questions, you can call 800-829-1040." I'm planning to mail in my 2021 return now, better late than never I guess. Based on my calculations, I should get about $4.1k back from that year. But my main concern is whether this will create problems with my 2024 refund processing. Will the IRS hold my current year refund until they process my late 2021 return? Will I face penalties that might offset any refund I'm due? Has anyone been in a similar situation?