Sometimes the server manager website is not accepting connections for a particular user it will result in the following error:
2019-04-13 10:59:11.6110 Error Ivara.PL.Client.WrapRemoteCalls [15] Exception caught EXCEPTION OCCURRED:CommunicationException An error occurred while receiving the HTTP response to http://APMServername:13101/DefinitionAssembler. This could be due to the service endpoint binding not using the HTTP protocol. This could also be due to an HTTP request context being aborted by the server (possibly due to the service shutting down). See server logs for more details.
This may be due to issues with the Server Manger Website itself.
Launch Windows IIS Manager and restart the Server Manager website. If this does not work, or the problem keeps recurring, check the "Set up Server Manager" section of the APM Installation_guide (page 80) and compare settings.