Device assignment: AssignmentTrigger::Set: can't open event (lastError=2), Errorcode=2

Hello,

We started to use the "device assignment" functions to add new computer devices automatically to the company's Contact List.
The first 8 computers aren't in the list after installing TeamViewer.
With a test machine, I experience the same: The entry in the Contact List isn't available.
We can connect to the TeamViewer Host with the ID and pre-set password, so connection to/from the client computer, is working well.

The TV Log file shows a lot of entries, I try to find the ones referring to this auto-assignment:

TeamViewer License: Corporate
TeamViewer Host setup: Setup file generated in the Management Console
Client: TeamViewer Host v15.0.8397 HC
Date: Nov 6 2019
License of this Host: Free
OS: Windows 10 Enterprise LTSC 2019

Command line for the setup:
X:\Staging\TeamViewer_host.msi /quiet /qn /norestart DESKTOPSHORTCUTS=0 IMPORTREGFILE=1 CUSTOMCONFIGID=$1abcd APITOKEN=$987-AbCdE0369 ASSIGNMENTOPTIONS="--alias ""%TVCITY%/%TVACCO% %TVFUNCTION% (%TVPREPID%)"" --group ""%TVCOUNTRY%/%TVCITY%/%TVACCO%"""

For security reasons, I replaced the config ID and API token.
The %% and quotes-stuff is translated well to the desired format, as reported in the TV Log file.
The TV Log shows for this entries the following result:
GroupName: BE/Test/Test
DeviceAlias: Test/Test Kiosk (1523)
Which is the expected result. So the command line for the setup, is working well.

The TV Log shows (I guess I copy/pasted at least some lines referring to assignment):
2020/04/17 12:20:07.646 1672 3848 C2 CustomConfigurationUpdaterImplWin::ReadInitialConfigurationId: Initial configuration "1abcd".
...
2020/04/17 12:20:07.802 1864 3948 C2 CommandLineTasks::Execute: executing task 'assign'
2020/04/17 12:20:07.802 1864 3948 C2 DeviceAssignmentStarter::Run:Start Assigment with parameters:
ApiToken: *****************************
GroupName: BE/Test/Test
DeviceAlias: Test/Test Kiosk (1523)
2020/04/17 12:20:07.802 1864 3948 C2!! AssignmentTrigger::Set: can't open event (lastError=2), Errorcode=2
2020/04/17 12:20:07.802 1864 3948 C2 DeviceAssignment::TriggerAssignmentAction - Try triggering the assignment event for the next 30 secs.
...
2020/04/17 12:20:08.818 1864 3948 C2!! AssignmentTrigger::Set: can't open event (lastError=2), Errorcode=2
2020/04/17 12:20:09.427 3904 6616 S0 LicenseTracker::UpdateMachineLicense() local license differs from master license
2020/04/17 12:20:09.427 3904 6616 S0 Non-Commercial use
...
2020/04/17 12:20:40.300 1864 3948 C2!! AssignmentData-File "C:\Program Files (x86)\TeamViewer\AssignmentData.json" didn't appear within 30 seconds, Errorcode=2


What is going wrong? What do we have to do, change, review, in order to get the assignment working?