Hi @Utilisateur ,
Hope you are doing well and thanks for the detailed report, and especially for listing what you've already tried, that really helps narrow things down.
Since a repair, full uninstall/reinstall, and a Cleaner Tool pass didn't resolve it, we can rule out a damaged installation. The pattern you're describing (stuck processes that block the next launch) usually points to something hanging around between sessions rather than the install itself.
A few questions first, since this is affecting three users and happening repeatedly:
Have you started experiencing this issue recently after the update or was this occurring earlier as well?
Are all three machines on the same OS version, and is the Acrobat version identical across them? Please share the version of the Acrobat App and the OS the users are using.
Does this happen after the app is closed normally, after a crash, or both?
Is this on physical machines or virtual desktops (Citrix, VMware, AVD, etc.)? That detail changes the troubleshooting path quite a bit.
In the meantime, please try the steps below on one of the affected machines:
Step 1: Capture what's actually stuck
Next time it happens, before killing anything, open Task Manager and note exactly which Adobe processes are listed (Acrobat.exe, AcroCEF.exe, AdobeCollabSync.exe, etc.) and whether any show unusually high memory or CPU. This tells us if it's a true hang vs. something waiting on a lock.
Step 2: Check for a stale lock or lock file
A common cause of "second launch silently fails" is a leftover lock file from the previous session that didn't clear. Have them check (and if needed, clear) the user-level Acrobat preferences/cache folder, since a corrupted preference file can cause exactly this kind of silent hang on relaunch.
Step 3: Look at background integrations
Since this happens randomly throughout the day rather than at every launch, it's worth checking what else is running alongside Acrobat, things like cloud sync clients (OneDrive, SharePoint sync), antivirus/endpoint protection doing real-time scanning of Acrobat's processes, or any DLP/security agent that hooks into PDF handling. These can hold a handle open on an Acrobat process and prevent clean shutdown.
Step 4: Disable third-party plug-ins temporarily
Launch Acrobat in safe mode (hold Ctrl while launching, on Windows) for a day and see if the issue still occurs. If it doesn't, a plug-in or add-on is likely interfering with process cleanup on exit.
Step 5: Check Windows Event Viewer
If it happens again, check Event Viewer (Application log) around the time of the failed launch for any Acrobat-related error or warning. That log entry, even just an error code, is often the fastest way to identify the actual root cause once we have it.
Since the Cleaner Tool + reinstall didn't fix it, my suspicion is this is being triggered by something outside Acrobat itself (security software, sync client, or VDI session handling), so the Event Viewer log, the Acrobat crash logs https://adobe.ly/4at5ygE and the answers to those three questions above would really help us pin it down.
Let us know what you find.
~Amal
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