Error [authenticating connection], Server websocket will be closed. cause: Application Key not fou

Hello,

currently, I am using Thingworx 8.2, Analytics Extension 8.2, Thingpredictor 8.2.

When I start the Thingpredictor the follwing error is shown in the Error Log:

Error [authenticating connection], Server websocket will be closed. cause: Application Key not found

I checkt the correct app Key twice in both files(predictive-standalone.yml,system-environment-variable.properties) and even tried it without any app key by commenting the corresponding line out.

In the Thingpredictor cmd Window I can see the following:

ERROR [2018-11-20 09:15:51,723] com.thingworx.communications.client.connection.netty.ThingworxClientConnectionHandler: WebSocket error: com/thingworx/communications/client/connection/netty/ThingworxClientConnectionHandler$1, closing connection!

It is still possible to publish models. But it is not possible to trigger events or jobs via setting different parameters of a Thing in Thingworc Composer.

What could be the reason for this?

Thanks,

Cedrik