You will see a big bump when you first launch Wavelength. A couple of weeks after launch, you will see the numbers go down. This is normal.
Wavelength isn't a tool that people need all the time. They need it when they are changing jobs or want to keep you updated about new information. This doesn't happen frequently. Your goal is to keep Wavelength top of mind, so that when they do have those needs, they know where to go.
If you want to increase activity, periodically promote Wavelength on social media, your website, and magazine. It should be the go-to-place for people to update their info. You should see up-ticks in usage when you promote it in these ways.