What do you mean he "immediately attempted to constrict, but after failing, he gave up completely."? Did he stop constricting the rat and it was still alive? Did he kill it and not eat it?

I just want to fully understand the situation.

In the meantime, I would stop removing him to feed in a separate bin, and zero handling until he is eating reliably. It just causes added stress which could be causing him to refuse food. Also, I wouldn't offer food so closely together, that is going to cause additional stress also. I would offer every 5 to 7 days.