Steam Error code 16 CoH2 Workshop Topic Closed!
1 cup of coffee and 1 cigerette solved the problem!
Here is the link
Troubleshooting Network Connectivity from the steam support that helped me after searching a while.
And furthermore the steam link to
Incomplete Installation Errors.
The Error code 16 seems to be caused by the Wireless LAN and/or the router and/or the anti-virus programme (in my case).
Here is what I did:
1. Disabled my anti-virus programme for 10 Min.
2. Opened Steam, CoH2 and published the map without problems via the workshop.
Thanks to Brummbaer for his reply!