Ok, this is weird. I have another 8-port switch directly connected to the 16-port switch mentioned above. If I connect the MT-1300 to the 8-port switch, it works!

Could it be an incompatibility with the 16-port switch? I tried 3 different ports on it. It’s a Zyxel GS1100-16. The 8 port is a TrendNet.Teg-s80g.

Is there a networking explanation for this?