Custom Action Validation not working/getting triggered for SAP standard Action in BOPF in SAP TM

For the SAP standard Action SET_EXM_STATUS_IN_EXECUTION (Set Execution Status to in Execution) of Standard Business Object /SCMTMS/TOR (Transportation Order) of BOPF in SAP TM, there was a need to add Action Validation. I have added the Custom Action Validation in the custom enhanced Business Object (in /BOBF/CUST_UI), but the Action Validation is not getting triggered/ not getting called when I am changing the Execution Status of the Transportation Order to 'In Execution' in NWBC.

The steps are same as mentioned Section 3.3.7 (Creating Action Validations) in the SAP Transportation Management 9.x Enhancement Guide. Also after creating the Action Validation, I tried manually calling the CHECK_ACTION method (as mentioned in the blog Navigating the BOPF: Part 4 – Advanced BOPF API Features) of the BO Service Manager to check if the custom Action Validation gets triggered but it also does not trigger the custom Action Validation.

Any help would be appreciated