Temperture in St. Louis has been 95-104 degrees. I have 2 EOC-3220+ units 1/4 mile apart. The EOC-3220+ is mounted on a 10FT pole and works well until we get over 90 degrees, then things get spotty. The unit is shaded in the morning and works reasonably well, in the afternoon, it doesn't work well.
So, I'm thinking about building a 5 sided box to give it shade.
I was once marginally involved in the design of a microwave radio system that eventually ended up on a pole in the middle of the Arabian desert. The primary method of cooling was a heat shield with convective cooling. The heat shield wasn't anything fancy. It was similar to the double roof on the old Land Rover series vehicles. See:
The first photo shows the "tropical roof".
In radio case, it was a piece of flat sheet metal, mounted on 4 thermal insulators, with one piece on each large face of the box. The flat plates got nice and warm, but the box underneath was sufficiently cooler to survive.
I almost forgot. Paint everything glossy white. That makes a huge difference in solar warming.
However, I think you may have a different problem. The Senao/Engenius boxes are not terribly energy efficient. They get quite warm. I'm not sure what it actually draws, but the power supply is rated at
48VDC 0.375A or 18 watts. It probably burns about 12 watts, which is quite a bit for the plastic box. What I think you'll need to do is find the major sources of heat on the circuit board, attach heat sinks or heat pipes to the components, and somehow get the heat out of the box and into the surrounding air. That's not going to be easy. If you can't do that, get a fan and use it to move some air through the box. You should also make some thermal measurements to see if you're making any progress.