Common Errors and solutions while running UiPath Robot

Error -1 
Source: Message Box

Message: Object reference not set to an instance of an object.

Exception Type: System.NullReferenceException

An ExceptionDetail, likely created by IncludeExceptionDetailInFaults=true, whose value is:
System.NullReferenceException: Object reference not set to an instance of an object.
   at lambda_method(Closure , ActivityContext )
   at Microsoft.VisualBasic.Activities.VisualBasicValue`1.Execute(CodeActivityContext context)
   at System.Activities.CodeActivity`1.InternalExecuteInResolutionContext(CodeActivityContext context)

Solution: Assign default value to the variable which is used in message box

Error - 2

An ExceptionDetail, likely created by IncludeExceptionDetailInFaults=true, whose value is:

System.Exception: Error opening workbook. Make sure Excel is installed. ----> System.Runtime.InteropServices.COMException: Retrieving the COM class factory for component with CLSID {00024500-0000-0000-C000-000000000046} failed due to the following error: 800702e4 The requested operation requires elevation. (Exception from HRESULT: 0x800702E4).

   at System.Runtime.Remoting.RemotingServices.AllocateUninitializedObject(RuntimeType objectType)

   at System.Runtime.Remoting.Activation.ActivationServices.CreateInstance(RuntimeType serverType)

   at System.Runtime.Remoting.Activation.ActivationServices.IsCurrentContextOK(RuntimeType serverType, Object[] props, Boolean bNewObj)

   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)

   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)

   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)

Solution: EXCEL.EXE was configured to run as administrator.

Remove this configuration to overcome this error.