I've had a similar issue like this before and had to use a different device to use this option.
Not sure why really.
There are also items that won't have financing as part of the payment options. Could be a type of promotional offer on the item or something to do with the value of it.
I've also had a situation where because I have finance with the company dealing with the finance. I wasn't eligible for another deal even though I have good credit. Just the rules they work by