IRS Notice CP504B, Notice of Tax Levy - penalty for missing Schedule K-1s

I am one of two members of an MMLLC and we filed Form 1065 for 2024, along with the K-1s as we normally do (the IRS acknowledges receipt of the tax return).  However, we received IRS Notice CP162B, dated February 23, 2026, showing a balance due from not including Schedule K-1 (which we did…they were stapled to the 1065 and the other related forms).  Unfortunately, that mail item was misplaced and we did not see it until months later.

We also received IRS Notice CP504B, Intent to Levy or Seize Property, dated April 20, 2026.  It says if the amount due is not received within 30 days, the IRS will take action.

We wrote a letter to the IRS in early May, stating that we included the K-1s in the original filing and we included the K-1s as an enclosure to the letter.  We have proof that the IRS received the letter.

It is now past May 20, 2026 and I have no idea what to expect next.  They have the K-1s along with our written request to remove the balance due.  I tried calling the IRS multiple times to request a stop to the collection process but their answering system keeps saying there is no one available to take the call and disconnects.

I am getting nervous.  The business does not have much in the way of assets except for the bank account.

Does anyone have any experience with this issue?  It seems our hands are tied.