It is likely that LinkedIn campaigns to warm leads (aka remarketing) could be a good fit, but LinkedIn campaigns to cold leads is only a good fit for a few narrow industries.
Some potential reasons are you are in a competitive industry, you have other key phrases that have proven to convert, there's low search volume, and where you are searching (Google) from.
A good remarketing strategy...
Testing & Double Checking Existing Setups...
Budget Strategies...