I failed to purchase the IRA by Midnight Monday the 18th of April. I submitted the Turbo Tax return on Monday. What can I do to remedy the failure to purchase the IRA timely???

pull the $4000 out + earnings or see if the trustee will move it to a 2022 contribution. of course in 2022 that amount would have to comply with the IRS contribution laws.

If you filed a return claiming a $4000 tax deduction for an IRA contribution, and then did not make the IRA contribution, you will need to file an amended tax return to remove the contribution and pay any extra tax you owe.

Since you just filed your original return, you will have to wait for it to be processed before submitting the amended return.  (That usually means waiting until you get your tax refund if you claimed one, or waiting 6 weeks if you owed tax.)

Here are some instructions to filing an amended tax return.

https://turbotax.intuit.com/tax-tips/amend-return/how-to-file-an-amended-return-with-the-irs/L6kO691J8

If you said you were contributing to a non-deductible IRA, you still need to file an amended return because it will change your form 8606, but you won't owe tax.  

If you said you were contributing to a Roth IRA, you don't need to file an amended return because you missed the contribution, unless you qualified for the retirement savers credit on form 8880. 

Any IRA contribution you make after 4/18/2022 will count as a 2022 contribution and not a 2021 contribution.