I am eligible to receive the advance child tax credit but didn’t get the first payment. It says pending in my portal and I’m not sure why because I got the letter.

[xmasbaby0]

We cannot see any of your information so we do not know what the portal is telling you or why you have not received the first payment yet.    This is a brand new system thrown together by the IRS after Congress changed tax laws in the middle of the tax season.  There are going to be bugs, glitches and mistakes made and folks will unfortunately have to be patient until they sort it out.  

If you do not receive the monthly payments you will be able to get the CTC on your 2021 tax return.

https://www.irs.gov/credits-deductions/2021-child-tax-credit-and-advance-child-tax-credit-payments-t...

[Critter-3]

According to the IRS if your return, even an amended one is still processing then  you will not receive the advance child tax credit payments.  Go to topic Q B 12  as of June 30th there were 35 million US income tax returns that had not been processed and estimated only 3% of phone calls were being answered. Verify that here