PS4 shareplay issue

See below, I was able to get it working for me on my rented Xfinity modem.

I figured out how to get this working. I had to turn on port forwarding.
This is a long and involved process for someone who knows a bit about networking, etc.

These instructions are very detailed. If you already know how to do this, I'll just list the ports that need to be forwarded. I found these on the Playstation website.

TCP: 80, 443, 3478, 3479, 3480

UDP: 3478, 3479

Detailed Instructions below:

1. Find the Mac Address of your PS4
--------------------------------------------------------
On the PS4 go to Settings -> System -> System Information
Write down the Mac Address for the network that you are using. There will be 2, one for Lan and One for Wifi. You will need this when determining which device you are port forwarding.

2. Find the Subnet Mask and Default Gateway of you internet
--------------------------------------------------------
You will have to do the following on a computer
Open a command prompt on your PC.
Enter the command: ipconfig
You should now see your Subnet Mask (should be 255.255.255.0) and your Default Gateway. You will need the IPv4 version of the gateway which will be in the form of ##.##.##.##
Login to your Xfinity account and select the Xfinity Xfi icon from the top menu.
Write these values down as you will need them later when setting up your PS4 network information

3. Setup port forwarding
--------------------------------------------------------
Go to xfinity.com and login (I recommend using a computer and not your phone, it is easier)
Click the Xfinity XFi link from the menu at the top
Click the Connect option (Overview, Connect, People, Home, More)
Click on See Network link
Click on Advanced Settings
Click on Port forwarding
Click the Add Port Forward button at the bottom of the page
Select the device. The name of the device will be the Mac Address you wrote down from step 1
Select Manual Setup
Enter Port Number 80, Select TCP and Click Next
You should now see this in your list of Port Forwards for that device (your PS4 mac address)
Here are the other ports that will need to be forwarded:
Port: 443 , Protocol: TCP
Port: 3478, Protocol: TCP/UDP
Port: 3479, Protocol: TCP/UDP
Port: 3480, Protocol: TCP
Write down the "Reserved IP Address" on this page. you will need it in the next step

4. Setup the network on PS4
--------------------------------------------------------
Go to Settings -> Network -> Set Up Internet Connection
Select Use Wi-Fi or User LAN Cable (I recommend LAN Cable if possible)
Select Custom for "How do you want to set up the internet connection"?
Select Manual for "IP Address Settings"
Enter the "Reserved IP Address" from step 3 as the IP Address
Enter the Subnet Mask and Default Gateway recorded from step 2.
OPTIONAL Enter Primary and Secondary DNS entries. Google and Open DNS are good options. You should be able to leave these at 0.0.0.0 though
I chose Google for my DNS. Primary DNS: 8.8.8.8, Secondary DNS: 8.8.4.4
Select Automatic for "MTU Settings"
Select "Do Not Use" for Proxy Server
Test your connection.
At this point your connection test should be successful and you should be able to use Shareplay.