Has anyone experienced over 21 days for tax returns? When should I start to worry?

I hear ya,today is 28 days for me. It said as first by the 18th. Now it says being processed since that day.

There's no way to know when the IRS will update the status of your refund. As your return moves through the system, the status of it will be updated accordingly. Continue checking the Where’s My Federal Refund?  tool for updates. Updates are made daily, usually overnight. You may also download the IRS2Go app to check your Federal refund status

If your return was accepted 21 days ago ( after opening day of January 27th, 2020 and excluding holidays) or more and you have not received an update via the Where's My Refund tool, you can follow the instructions in the following FAQ to contact the IRS for further assistance.

https://ttlc.intuit.com/community/refund-status/help/what-if-my-irs-refund-is-taking-longer-than-21-days/00/26080