I’m on level 30 - it says to visit storage. I have redecorated. How do I get to next level?

If you cannot get to the next level and the game says to visit storage, it means you need more flowers added to your island to proceed. On your island screen in the top right corner, next to your current level, it says how many more flowers are needed for the next level. Since it says to visit storage, it means you have the necessary flower value in your storage and just need to place them on the island to count. But if you lack the space for them, then you must acquire flowers in one of the other ways: buy decoration, renovate landmark, get from Jack's delivery. If you buy decoration, the flowers will not count until after construction is complete and the red ribbon is removed.