Get the ink flowing in a gel pen by scribbling until the pen works or by pumping the tip directly onto a few thicknesses of paper. Gel ink's high water content makes the pens prone to drying, which causes clogs and bubbling and disrupts ink flow.
The tip of a gel pen is a tiny ball that picks up the ink stored inside the barrel and rolls it onto the writing surface. The ball tip of a new pen needs to be rotated a few times before it picks up ink. An older pen that has dried or clogged needs for the ball to be loosened so that it rotates freely again. A pen with bubbles in its ink needs to have the air worked out to restore proper flow. All three issues can be resolved by scribbling with the tip or pumping it.
Prevent drying by storing gel pens with their caps in place. Keep ink flowing evenly by not shaking the pens or dropping them on hard surfaces, which may introduce air into the ink chamber and cause bubbles to form.
Sakura, a gel pen manufacturer, notes that a gel pen can't be unclogged by the heating or shaking that often unclogs the oil-based ink in ballpoint pens.