I can suggest a few things you can do to debug.
Have you actually got an scr implementation in your runtime? SCR (another name for declarative services) isn't included in Equinox core, so you'll need to include it. Most people use the Felix SCR bundle - it will sit very happily on top of Equinox.
Since Declarative Services just use services, you can change one half of your app at a time, to identify whether it's the service consumption or registration which isn't working.
You can also use the Equinox console to inspect your service registration. Use 'ss' to identify your bundle, then 'bundle [no]' to see what services are registered and consumed. If you're using Felix SCR, there are also Equinox console extensions, so you can use 'scr list' to see all services which a bundle attempts to register (and their state), and 'scr info' for more details on a particular service.