Acrobat updater appears to leave Windows Installer busy — configuration error 1602 and AdobeARM error 120100

Hello,

I need help diagnosing an apparently unfinished Acrobat update on Windows.

I am trying to install another application, VirtualBox, but my installation procedure stopped after detecting an apparently active Windows Installer transaction. I would like to establish whether Acrobat is still updating, waiting for user interaction, or encountering a recovery problem.

A read-only diagnostic collected on 13 October 2026 showed:

• Installed product: Adobe Acrobat (64-bit).

• Registered version: 26.002.21931.

• Windows Installer service: Running, with CanStop=False.

• Both AdobeARM.exe and msiexec.exe processes were present.

• The MSI InProgress registry key was absent.

Windows Application events recorded this sequence:

1. An Acrobat transaction started at approximately 16:49:26.

2. At 16:49:43, Acrobat reported “Configuration failed”, with reconfiguration status 1602, followed by a transaction-end event.

3. At 16:49:51, another transaction for the same Acrobat product started, with AdobeARM.exe as the client.

The AdobeARM logs also contain:

• “Another instance of ARM is already running.”

• “Setting Error Condition: 120100”

• An InstallProductMsp entry for:
  AcroRdrDCx64Upd2600221931_incr.msp

• Arguments: ARM_EXECUTION=YES REBOOT=ReallySuppress

The collected excerpt does not show the completion of that second installation attempt. Some ARM helper entries report ERROR_SUCCESS, but I cannot determine whether those refer to the helper or the actual Acrobat update.

The diagnostic itself did not stop processes, change services or registry settings, or launch another installer.

Could someone advise:

1. Which log or event would reliably confirm whether the second Acrobat transaction has completed?

2. How can I check for a hidden update, repair, or rollback prompt?

3. What is the Adobe-supported recovery procedure if this update is stalled, without damaging Acrobat or Windows Installer?

I do not have access to paid support. I can provide relevant, redacted log excerpts if needed.

Thank you.