@David-TP Thanks. Yes, this is the problem. Thank you for pointing out. Another problem is that the M5's router does not work as well as the TP-Link C7 router.

I recently installed Spectrum internet with 300 Mbps speed. If I directly connect my PC to the cable modem, it can indeed achieve 300 Mbps. However, when I connect the modem internet port to the Deco...