Paid Fed tax due with credit card through TT but IRS saying never received.

Paid fed tax with credit card via turbotax when filed on april 15.  CC statement shows was paid at that time. Received notice from IRS a few days ago that we are delinquent, according to their records we haven't paid anything and fees/interest are accruing.  I have now spent hours and hours on hold or on phone/video call with turbotax, they were unable to help, said this was happening to other people as well.  Gave me number of what I guess is the 3rd party payment collector, FSI (or FIS, not sure), told me I had to call them.  I did, there is STILL a message about COVID causing delays in response time, and then waited exactly one hour and 45 minutes on hold before hanging up, concerned that maybe no one will ever answer.  Called the IRS, on hold 1 hour 29 minutes but someone answered!  IRS said they definitely don't have the funds we paid, and that the only way to prove we paid is with a "CONFIRMATION NUMBER" from turbotax.  IRS said that if I just mail in the receipt/proof paid from my bank it might not be enough, 'must have the confirmation number.'  However, it seems that Turbotax cannot provide this.  Where is this magical confirmation number?