I had the same code R7404 on my Bobcat 2014 T650, the cause that I found was a rubbed wire from one of the switches on the hydraulic pump. I spliced the wire and soldered the connection poblem solved.
The only electrical operation of the heater is the blower motor, you stated that your heater wasn't blowing hot air nothing to do with the electrical function.
I have the same problem, 2014 Bobcat T650 Kubota motor, fuel pump working, battery fully chargrd, fuel solinoid omes out OK. I'm stuck. I've been reading the OE shop manual over a few days performed all fuel related test all check out OK. Any Idea?