oh my god, I found the problem..
I've set up the synch folder in my dropbox. But Dropbox added (in the dropbox business accounts) a new feature "Smart Synch" what store the data only in the cloud. So the preferences were added but there were only in the cloud and not stored locally. I think Alfred wasn't able to get the preferences and so it got no workflows.
After change the synch-Folder to an local folder its working fine like before. :-)
So, much thanks for your help!
Greetings from Germany