If the jacket is still waterproof then just use something like Nikwax techwash or Grangers wash and proof (You can also use pure soap flakes and handwash in cold/lukewarm water instead)then leave to drip dry (dont put it on a radiator).If this doesn’t work then use the waterproof restorer as well but in a second wash cycle.
whatever you do DONT use normal washing powder/liquid (it contains bleaches which will remove all the waterproofing treatment or fabric softener which will just screw up the fabric.
For the above reasons if you are machine washing clean out the detergent tray before you start.
If you have eVent jacket then once the jacket is dry, give it a once over with a warm steam iron (use a teatowel so you dont damage the jacket)as this brings back the full waterproofing. Works a treat.