How can I cast on with my knitting machine new needles?

I have just got my Brother KH840 out of storage after many years. I have cleaned it and it seemed to be working well but the needles were a bit rusty. Purchased 50 new needles from Amazon and replaced them yesterday, from 0 to 25 either side of the centre. They are supposed to be for the KH 840!
No matter what cast on method I try it will not cast on using these new needles! The yarn goes straight across the needles without going round the bars.
Help please!