I had the same problem in the past 18 months even with my accountant writing letters to support me the whole way. Only, my mistake was making a single monthly tax deposit in 2019 marked Q2 instead of Q3.
irs threatening to lock all my bank accounts (oh how I would love to get stuck overseas with no friends or family where I am and lose all access to money). Exorbitant penalties, and I can easily get them on the phone - only the person I spoke with had an IQ so low they replied to everything I said as if they thought I was mentally handicapped. The phone call was beyond worthless.
irs threatening to lock all my bank accounts (oh how I would love to get stuck overseas with no friends or family where I am and lose all access to money). Exorbitant penalties, and I can easily get them on the phone - only the person I spoke with had an IQ so low they replied to everything I said as if they thought I was mentally handicapped. The phone call was beyond worthless.