Does anyone know how to fix this error: Failed to connect to PC service?

Details:

Receiving this error when executing a scenario from the "Test Plan" module
Selected a scenario and clicked "Run Test" > Click "OK" to "Select Test Instance"
> Select "Run" from " Select Timeslot" and the error occurs

All Required Services are running:

For the Performance Center Server (PCS):
– Data Collection Agent
– Remote Management Agent Service
For the Load Test Server (LTS):
– Data Collection Agent
-RemoteManagementAgent Service
-Performance Center Agent Service
-Performance Center LoadTesting Service

The PC event log Shows this

Message:
Failed to connect to PC service; Failed to start load test id 4, run id 21. Failed to insert new run to database;

Stack Trace:
> com.mercury.td.pcprojectextension.pcexecutionmanagementservice.comm.IPCExecutionManagementRunLoadTestInsertPCRunFaultFaultFaultMessage:
> Failed to start load test id 4, run id
> 21. Failed to insert new run to database
> at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native
> Method)
> at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
> at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
> at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
> at com.sun.xml.internal.ws.fault.SOAPFaultBuilder.createException(SOAPFaultBuilder.java:130)
> at com.sun.xml.internal.ws.client.sei.SyncMethodHandler.invoke(SyncMethodHandler.java:108)
> at com.sun.xml.internal.ws.client.sei.SyncMethodHandler.invoke(SyncMethodHandler.java:78)
> at com.sun.xml.internal.ws.client.sei.SEIStub.invoke(SEIStub.java:107)
> at $Proxy215.runLoadTest(Unknown Source)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native
> Method)
> at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at com.mercury.td.pcextension.comm.PCRetriableProxy$1.invoke(PCRetriableProxy.java:102)
> at $Proxy216.runLoadTest(Unknown Source)
> at org.hp.qc.pcprojectextension.pcrun.PCRunLogic.executeRunCallToPC(PCRunLogic.java:570)
> wrapped in com.mercury.optane.core.CTdException:
> Failed to connect to PC service
> at org.hp.qc.pcprojectextension.pcrun.PCRunLogic.executeRunCallToPC(PCRunLogic.java:589)
> at org.hp.qc.pcprojectextension.pcrun.PCRunLogic.startRun(PCRunLogic.java:206)
> wrapped in com.mercury.optane.core.CTdException:
> at org.hp.qc.pcprojectextension.pcrun.PCRunLogic.startRun(PCRunLogic.java:227)
> at org.hp.qc.pcprojectextension.pcrun.PCRunLogic.executeRun(PCRunLogic.java:650)
> at org.hp.qc.pcprojectextension.pcrun.PCRunLogic.executeRun(PCRunLogic.java:614)
> at com.mercury.td.tdserver.requests.StartRun.execute(StartRun.java:20)
> at com.mercury.optane.core.web.RequestsDispatcher.execute(RequestsDispatcher.java:90)
> at com.mercury.td.web.CAbsServlet.executeFunction(CAbsServlet.java:483)
> at com.mercury.td.web.CAbsServlet.processRequest(CAbsServlet.java:475)
> at com.mercury.td.web.CTdServlet.processRequest(CTdServlet.java:165)
> at com.mercury.td.web.CAbsServlet.doPost(CAbsServlet.java:349)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
> at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
> at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
> at com.hp.qc.core.utils.gzipfilter.GZIPFilter.doFi