If you are getting a refund there is no penalty for filing late. You have three years to file a tax return for which you are receiving a refund.
If you owe tax due and did not file an extension then you are just late and should file as soon as you can and pay your tax due. Your late filing penalty and interest began to add up after May 17 if you owe tax. TurboTax will not calculate that--it will be calculated by the IRS and they will bill you for it.
Can I file for an extension now?
No, the deadline for filing an extension for tax year 2020 was May 17, 2021.
If you have taxes owed on your return you need to file as soon as possible since penalties and interest on the unpaid taxes will continue to accrue until the taxes are paid.
If you do not have taxes owed or have a tax refund there are no penalties for filing after the due date of the tax return.