If you filed by mail that could be 98% of the explanation. If you mailed it in this year the IRS was undermanned to deal with mail and it will take a long time. See this article on line:
https://grow.acorns.com/irs-tax-return-delays/?s1=google_performance_max&gclid=Cj0KCQjwweyFBhDvARIsA...
I had one year where I waited for almost 6 months to get my state refund and roughly 3 months for the Federal. Some suggestions:
1. always efile
2. don't pay them more than you owe--see below
3. If you have any questionable items provide enough information so that they can understand what you did and why
4. Pay your estimated taxes out of your IRA if you are taking mandatory distributions. You can allocate 100% of an IRA payment to taxes and IRA payments made on 12/31 count as timely made for estimated tax purposes (penalties and interest) and by 12/31 you should have a much better handle on how much you owe
