what was the format of payment - check, money order, electronic payment ....?
how did you make the payment? mail it in with 1040-V and identifying info on payment such as year SSN etc
or use direct debit? did you specify a date if you used direct debit?
you can use this IRS website, after signing up, to check up on your payment but if it hasn't been processed it won't show.
https://www.irs.gov/payments/view-your-tax-account