The settings for all three Macs, and an iPhone are the same. They are linked to the same account.
But that does not ensure, that My Photo Stream will show the same photos on all devices. It is perfectly normal, that you are seeing less photos on a device, where you enabled My Photo Stream the first time.
Get help with My Photo Stream - Apple Support
Your device keeps up to 1,000 photos, even if they're older than 30 days. Photos older than 30 days are removed from the iCloud server, so depending on when you enabled My Photo Stream, your devices might not have the same photos. Due to capacity, your Apple TV might display only your most recent photos.
What is the format of the photos you are not seeing in Photos on your macOS 10.13 Mac? Photos supports less image formats than iPhoto.
Is the My Photo Stream album empty, or are you not seeing it at all?
The My Photo Stream album will not be visible, if iCloud Photo Library is enabled.
And Photos on High Sierra will only download photos from iCloud, if you are connected to Wi-Fi. A cellular connection or ethernet may not work. Is a VPN active?