@Raikke,

No problem with the translation here, hope my reply translates OK.

Was thinking, might want to try booting into SAFE MODE WITH NETWORKING on one of the W10 PC's. Not always easy to do, but the steps are not hard. See https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode how to do it. Probably will not help. but worth trying?

Wondering is there is an ACCESS CONTROL problem? Does the router have a Whitelist for Access? In the Emulator for the device it seems you can do MAC Fitlrering to allow access? Could also try IP and MAC BINDING for one of the W10 PC's?

You might just be able to get some hint at to 'why' in the log of the CPE510 too? Have you looked at that? Maybe doing a PING from the PC to the CPE510 and look for entries?

Like I said, I don't work for TP-Link and I don't have your h/w, so I am just suggesting some debug stuff I'd try?