Hi @Karandeep_Singh,
if you want to invoke a tenant specific decision definition from a shared process definition then you have to set the tenant identifier explicit on the business rule task. For example:
<businessRuleTask id="businessRuleTask" decisionRef="myDecision"
camunda:decisionRefTenantId="${ execution.tenantId }">
</businessRuleTask>
Does this help you?
Best regards,
Philipp