I've tried creating a simple workflow to change the case status from "Resolved" to "Reopened" when a customer replied to the case. I've found a few guides online to do this but for some reason it doesn't appear to function.
Here is the workflow rules: 
And here is the workflow action: 
Debug log:
10:29:37.217 (217367041)|CODE_UNIT_STARTED|[EXTERNAL]|Workflow:EmailMessage 10:29:37.217 (231870417)|WF_RULE_EVAL_BEGIN|Workflow 10:29:37.217 (231915699)|WF_CRITERIA_BEGIN|[Email Message: 02s1D000000PBXs]|Email Message Test|01Q1D0000007b3K|ON_CREATE_ONLY|0 10:29:37.217 (235993912)|WF_RULE_FILTER|[Email Message : Is Incoming equals true] AND [Case : Status equals Resolved] 10:29:37.217 (236022204)|WF_RULE_EVAL_VALUE|false 10:29:37.217 (236029789)|WF_CRITERIA_END|false 10:29:37.217 (236047673)|WF_CRITERIA_BEGIN|[Email Message: 02s1D000000PBXs]|Email_Message_test3011D000000BSAn|01Q1D0000007azX|ON_CREATE_ONLY|0 10:29:37.217 (236230003)|WF_FORMULA|Formula:ENCODED:[treatNullAsNull]true|Values: 10:29:37.217 (236241493)|WF_CRITERIA_END|true 10:29:37.217 (236801664)|WF_SPOOL_ACTION_BEGIN|Workflow 10:29:37.217 (236838041)|WF_ACTION| Flow Trigger: 1; 10:29:37.217 (236844210)|WF_RULE_EVAL_END 10:29:37.217 (261839312)|WF_FLOW_ACTION_BEGIN|09L1D0000000sKi 10:29:37.217 (261899102)|WF_FLOW_ACTION_DETAIL|09L1D0000000sKi|[Email Message: 02s1D000000PBXs]|Id=09L1D0000000sKi|CurrentRule:Email_Message_test3011D000000BSAn (Id=01Q1D0000007azX) 10:29:37.217 (262376078)|WF_FLOW_ACTION_DETAIL|Param Name: myVariable_current, Param Value: ENCODED:{![treatNullAsNull]{!ID:this}}, Evaluated Param Value: {Entity type: EmailMessage, id: 02s1D000000PBXsQAO}|Param Name: myVariable_old, Param Value: {!old}, Evaluated Param Value: null 10:29:37.217 (267526558)|WF_FLOW_ACTION_END|09L1D0000000sKi 10:29:37.217 (267646688)|WF_ACTIONS_END| Flow Trigger: 1;
Would anyone perhaps know why this isn't functioning or know of an alternative method?
