Most people believe when romantic love is lost, it is impossible to restore. But this is not true.
It doesn't sound very romantic, but what most of us call love is an emotion; emotions rise and fall according to what we are doing for one another, or with one another, to produce the emotion.
When couples say, "I don't love you any more," what they are confessing is that they have stopped doing the things which produce the emotions of love.
More importantly, if you start doing the things again which produce the emotion of love - even if you do not feel like doing it, love will return. Try it.