First look at Form 9325 in the clients file and see if it shows they were accepted....then you can call the EFW automated number and inquire about the payments to see if they are in the system

https://www.irs.gov/payments/pay-taxes-by-electronic-funds-withdrawal

Call IRS e-file Payment Services 24/7 at 1-888-353-4537 to inquire about or cancel your payment, but please wait 7 to 10 days after your return was accepted before calling.