Sometimes my fleet won't warp after leaving the base, is this a glitch or am i doing something wrong?

Does seem to happen sometimes, try sending your fleet outside the outpost first before sending it via warp

To use Warp you need 'Warp Coordinates'. The only ways to get Warp Coordinates is via an established Outpost, Union Member's Base/Outpost, or some other deployable.

Sans Warp Coordinates, your ships will default to Cruise. Your Cruise speed is vastly slower than Warp speed.

The game will automatically use the most Direct Route to your end destination. You can choose alternate routes on the bottom left of your screen, when selecting a destination, however if there is no other viable route, then nothing will show.