How do you re-proof helly hansens?

my daughter bought a helly tech helly hansen coat bacl last year, it was waterproof and windproof, when we washed it as said at 40 and not to tumble dry it became less waterproof and now she cant wear it in the rain as it is no longer waterproof, she has been into shops e.g (go outdoors,millets) and asked how to re-proof it and they all said the re-proofing wash in and spray but it says it is heat activated and the label on the coat does not allow heat... how can i re-proof it??? without waisting the coat and buying a new one?|||you can get a spray to waterproof it with, just dont use real high heat