Made a huge cake but icing won't set, any tips?

[pinkrocker]

Made a 6 tier rainbow cake using recipe from Mima Sinclair's Rainbow Bakes book. www.amazon.co.uk/dp/0857833898/ref=cm_sw_r_other_apa_i_OZRZEbFXH6QGV?tag=mumsnetforu03-21
I followed the recipe exactly but I've a good third of the icing left and it won't set, any tips? It's to share with all my neighbours tomorrow so I can leave in the fridge til then.
(Obv I will be SD responsibly and will have it cut into slices on paper plates!)

What ingredients are in the icing?

800g cream cheese, butter, icing sugar and vanilla

I'm not sure those ingredients will set at all. It's just a butter/cream cheese type icing. Do you mean it's completely liquid? In that case just add more icing sugar, but you might need a lot

There’s not nearly enough icing sugar in the recipe for that to set. For piping cream cheese icing I use 225g cc / 75g butter / 450g sugar. That would round up to about 2.4 kg icing sugar in your recipe!

It’ll taste lovely, but be quite runny.

It's kind of squishy, I thought it might set hard but it doesn't. It's been in the fridge for 2 hrs. I can add icing sugar to what's left in the bowl & put it in tomorrow, but it's already got 1kg of icing sugar in it!

@magicstar1 it does taste ok but slightly, slightly bitter. More icing sugar then! Ta.

Sometimes over-beating cream cheese turns it really runny it's really tricky to get it thickened up once that's happened. I know it's not much use to you now unless you have spare ingredients to make anothers batch... next time cream the butter and sugar and vanilla together and then gently fold in the cream cheese, that usually works for me

Hi, no I haven't any spare, this was the culmination of 3 x shopping trips to get enough icing sugar hopefully people won't mind it being a bit squidgy.

If it's only icing sugar you need more of, you can blend granulated sugar until it's powdered and that works too :)

I'm sure it'll taste lovely regardless

Thank you everyone for your advice.
It's been sat in the fridge all night, still squishy and hasn't set, it's like the texture of buttercream. I shall just tell people it's meant to be like that !