You are probably using URL shortener (services as bit.ly) or other redirecting services.
The Google Analytics tracking parameters are attached to the shortener URL and, when the redirect occurs, the parameters are dropped (as they were attached only to the shortened URL) and not passed to your Website - so they are not reported to your Google Analytics.
The only solution here is to add your tracking parameters to the URL you use in the URL shortener, but of course they won't be changed dynamically. Otherwise, you can try to look for a redirecting service that will pass your tracking parameters.
--- UPDATE ---
Due to requests about what kind of services are available on the market, we are providing Tiny.cc as an example of URL shortener of this type.
Make sure to properly read instruction when using this kind of service. For example Tiny.cc need you to add a
/ to the end of the generated URL to make sure your extra parameters are sent
Tiny.cc free service can be very slow, so we highly recommend to get a pro account if you intend to use this service.
Other services are available on the market, so feel free to explore around: you only need to ensure that parameters are passed to the destination URL.