Hi Julia,
like Amy, Ive always used Lowans whole grain rolled oats too.
I often have porridge for my brekkie and for a single serve I make mine as follows
I don't use milk in my porridge, I heat a small amount in my Nespresso milk frother and add on top along with a light sprinkle of rapadura sugar or raw honey - yummo....sultanas always come out whole when using reverse
230g water
40g rolled oats
A few sultanas
1/2 tsp vanilla extract
can add a pinch of salt (I don't)
Cook 7 mins / 90oC / reverse / speed 2
If DH wants it too, I just double ingredients and cook 9 mins
Haven't ever had it undercooked, so not sure what would be the cause, can you perhaps check the TM temp with a food thermometer just to make sure it's coming up to temp?
Really don't know why it's not cooking, maybe try another packet of Lowans or another brand would be a good comparison?