I’m afraid this has been covered pretty extensively in another forum thread…
https://forum.gl-inet.com/t/wifi-association-issues-on-chromebook/7893
Alas, gl-iNet doesn’t have an Acer chromebook (or any of the other models where the problem has been replicated) to troubleshoot.
Restarting the router is pretty much a waste of time. The problem exists between the MT300N-v2 and Chromebook and not a router the mango might be connected to.
Best advice if you really need to get this working is that maybe 1% of the time you’ll get connected. Or buy a Slate or try some other model.