I faced the exact same issue. Before enabling the plugins follow the below steps. Make sure you are running the commands in RabbitMQ Command Prompt using Administrator privilege. Hope your issue will be resolved.
Command 1 (By this existing service will remove) --> rabbitmq-service remove
Command 2 (By this new service will add) --> rabbitmq-service install
Command 3 (By this you can enable the RabbitMQ management UI plugins) --> rabbitmq-plugins enable rabbitmq_management
