So, last week I setup a Deco M5 mesh network in my home. Works great. However, the base deco only has two ethernet ports - one for incoming internet from my modem and one for other devices - of which I have a few. One of them is a Linksys PAP2T for my VoIP service. With that plugged straight into the deco, it works. With that plugged into an old 100Mb switch which is in turn plugged into the deco, it works. However, with that plugged into a TL-SG1005D which is in turn plugged into the deco, it does not work. What? How does a switch in 2019 not work with VoIP? Please advise!

-jonathan