If you raised a $15m Series B, these days, it’s quite possible a small amount can be used to buy out your shares.
Don’t expect an amazing price, but the company can raise another $1m and use that at least in part to buy you out. These days, most Series B investors are OK with a small bit being used this way, and if the company was able to raise $15m, it can probably get another $1m.
But expect a price that is lower than the preferred price in the round, and potentially materially lower. If you are OK with that, ask nicely, and see what happens.