Just an opinion here based upon what you've described and my own experiences:
As a child, my family moved around a lot, different schools, I was frequently the "new kid" in school with all the stress from that, different houses, different environments. Throw in an ASD condition (undiagnosed at the time), with the usual sleep disruptions, anxieties, laying awake mind racing over this and that. I was exhausted and stressed.
Well, now, I know a few facts. The autistic brain is often working "overtime" due to an excess of excitatory neurotransmitters. The brain keeps firing away, leading to repetitive and intrusive thoughts, special interests, and even physical effects like "stimming". Many of us have enlarged amygdala's (fear centers), and I don't know what came first, "the chicken or the egg" here, but the social and emotional processing centers are often altered leading to underlying anxieties and depressive states. This is sometimes "subclinical", but present, nonetheless. The brain, at some point, will become overwhelmed and try to protect itself by selectively shutting down "non-essential" functions. What we see is first, the signs and symptoms of stress, "autistic burnout", followed by what we call an "autistic shutdown". As an adult, I can pick up on these signs and symptoms, and need to self-regulate with self-imposed "time outs". So, at work, for example, I might slip away into a break room, rest room, or locker room, take 10-15 minutes, "chill out", grab a drink, relax, then go back to work. As a child, what you may witness is "avoidance behaviors" of one form or another.
All I can suggest is that he did his best for the first 2 weeks, now his brain is has had enough and needs to rest and regain its composure.
Helpful things on your end will be to look at his diet, as the "gut-brain axis" does play a role. Don't try to eliminate, but do practice some sugar/carbohydrate restriction. Carbohydrates cause insulin spikes (causing cerebral vasodilation) and are pro-inflammatory (cerebral edema), so NOT having that pressure inside his skull will help. A broad-spectrum probiotic will often help over the long-term. L-theanine is a good over-the-counter supplement that increases the uptake/conversion of glutamine/glutamic acid (one of the primary excitatory neurotransmitters). GABA can help the gut, and to a lesser extent, the brain (as it has a difficult time crossing the blood-brain barrier).