Only the IRS can answer that, as they do not advise TT.   Could you have made a data entry error, or forgotten to claim some income?   Also see this:

Why is my IRS tax refund delayed 2021? Report offers clues (fastcompany.com)

We have called the irs 3 times each agent said it’s turbo taxes fault on how they filed our taxes.  I’ve used turbo tax for 20 years this is the last.  They screwed up our 2nd stimulus check now this.  We are done!!  Millions of others are too I’ve been following the threads!!! Maybe if they have to pay us all back millions for making us wait they will learn.  Don’t mess with peoples money during a pandemic!!! 

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@alray2016 wrote:

We have called the irs 3 times each agent said it’s turbo taxes fault on how they filed our taxes.  I’ve used turbo tax for 20 years this is the last.  They screwed up our 2nd stimulus check now this.  We are done!!  Millions of others are too I’ve been following the threads!!! Maybe if they have to pay us all back millions for making us wait they will learn.  Don’t mess with peoples money during a pandemic!!! 

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What exactally do they say is wrong?   What is the error?