Yeah, I've had this problem several times before over the years. After refreshing the game the bonus game would usually recover back to where it stopped, with the frozen spin already done and counted for.
On rare occasions, the entire bonus game would have been completed by itself and any additional wins from the remaining bonus spins would have been added into your balance.
However, if the bonus game does not recover again after refreshing the game, restart your game from the lobby one more time and this would usually recover the frozen bonus game.
If none of the above works for you, then you need to inform the casino and they will refer the case to the game provider for a solution. This will of course cause a delay of several days if not weeks!