How

There is nothing you can do to force adverts to appear in your game @roo5

If you have lost them after making a purchase with real money then you will not see them again for at least a year, but there is a chance you will never see them again.

If you haven't made a purchase, but your adverts have stopped working then this is normal as well. Sometimes the adverts will come back after a short time, but sometimes they never come back.

I once lost my adverts for seven months

I am sorry to hear that @roo5

Boosters from the adverts wouldn't necessarily help you win the Music Festival though. The person that wins Events like these are the people that can play twenty four hours without stopping.