My male also does this, his environment doesn't change at all but sometimes he eats with no issues and others he seems almost afraid of the rat (f/t of course) and he will tend to ball up and protect his head as if the rat will hurt him. What gets me is that it seems totally random with him, one week he will eat then fast for 2-3 weeks then back on feed for 2 weeks then fast.

If you find any tricks to get him to take please share, he and the female are in shed though so I doubt they will eat tonight.