You shouldn't need an Environment Variable (aka setenv).
By default it should negotiate up to 1Gbps... I have dozens of deployments doing that out-of-box. If you issue 'purge' then the AP is out of box config and that should work...have never had to modify it from that mode.
DO you have other AP-105s that are working OK? (aka. can you try another one on same port etc and see if that has same result?)
POE switch would be the best bet as it keeps-things-simple (KIS) of course.... which I see you have tried in vain.