Possible reasons for non-slump
Too low a temperature for the size of the mould.
Too short a soak (i.e. none) at the top temperature.
Your top temperature is at the low end of slumping temperatures, so you need a long soak. The smaller the mould, the greater the time it takes for the glass to slump – weight and gravity apply. As I don’t know the size of the mould or its shape, nor the size or configuration of your kiln, I can’t really be more specific.
I do have a range of suggestions in my blog, though. use “slumping” for the tag.