I didn't replot the route. Don't know how to do that. I brought up the galaxy map and typed the name of the system I just came from and it highlighted, then both the mark and plot route were red.
I must admit that I get that sometimes. I close the galaxy map and open it up again, which seems to sort it out. there seem to be all sorts of glitches in the game at the moment.
Go to oufitting and check what your jump range is, then compare that with the distance that the galaxy map says the jump is. Obviously, you can't jump if you don't have enough jump range, so you have to figure out why. Either your mass increased or you changed your FSD. You can improve your jump range by reducing your ship's mass or improving the FSD. If you have enough jump range, but still can't jump, it's either a glitch in the plotting or you lost permission to go back.
You need to be more specific. Where are you trying to jump from and to, and what ship and loadout do you have, then we can get straight to the bottom of your problem.9 times out of ten, there's a logical explanation. without specifics, all we can do is guess.