Hello Hari
You will have to configure extended notifications for reminder emails for pending approval work items. This is system configuration and is applicable for all workflows. Refer to detailed knowledge base article below
https://service.sap.com/sap/support/notes/1646056
For configuring the WS20000075, ensure that this WF is active in SWE2 ( BOR BUS2012 EVENT RELEASESTEPCREATED Receiver WS20000075) and all the dailog tasks are set to "general task" and release strategies are configured properly. Reach out to MM consultant to ensure that SPRO configuration is maintained correctly. Activate WF template WS20000075 in SWDD.
Few links for your reference
Multi-step "WS20000075" workflow send to ALL the validators
Standard Workflow template WS20000075 Version/Repair Request
WS20000075 - multi level approval
Regards
sandy