Provisioning causes loss of local network connection

[LouSmith]

We set up on an OVH vps that works fine with Windows softphones as well as both android iphone clients.
However, the 3 Yealink T42S deskphones (new but have current firmware installed) using STUN are a total bust.
All are configured according to 3cx training videos but, after the phone is configured in the console and rebooted, the phone loses network connectivity.
SIP ports are 5065, 5066 and 5057
RTP port ranges follow the same process: 14000-14009 etc
IPs are static assignments and work properly until provisioning is attempted.
Internet is Spectrum cable;
Router is Netgear R8000P;
Switch is Netgear M4100-D12G and has been configured using their "Auto-Voice" VLAN as well as a manually configured voice VLAN based on their exact instructions. Neither have any effect on the provisioning problem so I have no idea which approach would be best.
Defective cables have been ruled out and changing the phones made no difference.
This is my first pbx even though I've been around technology for over 50 years. I would really appreciate some help. Experience in other areas tells me that I'm missing something very simple.

 

[LouSmith]

It's interesting that the switch has a bad port and I was going to return it anyway but, you're right, it has been a huge learning experience. If I were 50 years younger, I would keep it for a learning toy but I'm a recovering perpetual student who needs to focus on the job at hand for the next few months.
I think I'll go with the Dratek because the site is currently 100MB but is likely to go to 200 or even 300. I was surprised that my normal distributor TechData doesn't stock Dratek so I guess I'll just get it at Amazon.

 

[lneblett]

You are correct, the distribution channel is not that broad. They are more prevalent in Asia Pacific and the EU than in the US. Being a reseller, I obtain them thru a distributor ABPTech located in Dallas. They also handle 3CX as well as the other SIP enabled and networking products.