The amount the TPG refunded me was short? Any reason for this?

[VolvoGirl]

How much is missing?  A common reason is you claimed the Recovery Rebate Credit on line 30 or too much Child Tax Credit on line 28 but the  IRS had already sent it to you.

1,400 or 2,800 (or multiples) is the 3rd Stimulus payment.  Did you already get the Stimulus payment they sent out last year starting March 2021? The IRS has records that show you were sent the 3rd stimulus payment so they removed the $1,400/2,800 Recovery Rebate Credit.

 Do you have an amount on 1040 line 30?  You might have tried to claim it again.   Line 30 is only if you didn't get the full amount or qualify for more. 

Double check your bank statements and check your IRS account (both accounts if married) to see what they sent you.  Check both IRS accounts if married.

Your Online Account | Internal Revenue Service

[Critter-3]

Did the IRS send less ... check there first :  https://www.irs.gov/refunds