I’m very frustrated with using their app today: I’ve been on checkout and it’s greyed out and not allowing me to proceed to pay

I’m very frustrated with using their app today: I’ve been on checkout and it’s greyed out and not allowing me to proceed to pay. I went to help and it indicated that I must ensure that the delivery surbarb is same as cart. I’ve done all that and it’s still greyed out. I’ve been using the app many times I’ve never experienced the problem before.