I have a few dumb devices (Gemtec IoT LoraWAN gateways) on one network that rely on NTP to function correctly. After they were installed, they worked for about 1 day then stopped relaying sensor info ...

IIRC windows doesn't run ntp by default, it runs some propretary w32time service instead. I think it has an ntp client built in, but I'm not sure if it can be an NTP server out of the box.