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Make sure your web server correctly responds to REST / HTTP requests and the port of your web server is open in Firewall. Make sure the WCS server app is correctly configured for the REST URL of the web server, and WCS Manager logs do not have server logs contains no errors. Besides, you can turn off using REST completely with the remove app-rest-method command. In this case there will be no requests to the web server and corresponding errors. And the web client will have tp pass all necessary data to itself as described in the REST hooks section.