I made 1 estimated tax payment for a very small amount on 2020 taxes because I thought my situation might warrant needing to pay more than was being withheld, and other situations that changed. I made it online with the IRS app. Then I found that I could just have any additional amt withheld above and beyond. I knew I didn't need to do this anymore and didn't make any more payments. I totally forgot about it and filed my taxes and its been over 30 days. Online it was accepted, but shows "Still being processed". Could this be the reason, or will this cause me any issues because I made that estimated payment early in 2020 (April). I don't owe and I'm due a refund and paid taxes all throughout the year like all other years "paid as I made". I created an account and checked my transcript and it does show I have that amt as a credit along with stimulus payments that were made for the 2020 year.
Not necessarily. You may just need to wait a bit longer as the IRS has had to implement many changes in the last few weeks. Trying using the following link to track your refund.
IRS processing time and refund status
The online link is your best option to track your refund. I have attached a link with more answers from the IRS as to why your refund may be taking longer to process.