Manual here: http://www.whiteknightrange.co.uk/assets/index/download/id/2655/
It does talk about a cut-out that may operate if the machine isn't kept clear of fluff but doesn't mention a reset button.
See this FAQ page form White Knight, however:
https://whiteknightdryers.com/faq/
If there is no cutout then, as "Good Luck" says, the heater may be duff.
acp, April 2017