how do I order prints from Photos?

Open the Photos > Preferences > General. Set the country for the Print Products Store to the country where you are living. Then go to the Photos menu > Print Product Store account and set the details for your billing address and shipping address. The need to be in the same country.

Now select the photos you want to be printed in Photos and use the command "File > Order Prints".

See this Help page: Order professional prints of your photos in Photos on Mac - Apple Support

etc phoned Apple support and he knew nothing about this message or the demise of the printing

They really should know better. 😟

Send Apple Support a link to their own Support Document:

https://support.apple.com/en-us/HT208930

I use Photos and managed to send ( after three attempts) a project and received it last week.

This week I have tried to send another one - have tried unsuccessfully about 10 times and get the same message as you. I updated my Mac , same payment details, etc phoned Apple support and he knew nothing about this message or the demise of the printing

I’m so disappointed that Apple discontinuing print service ( so good when it works!) I wonder if the issue with connection is because everyone trying to order!

I have checked out all the suggested options and they all look inferior for ease of use/ editing/ delivery to countries other than USA

Did you preview the book, to make sure, that Phtos can render the PDF file correctly? If not, check the preview for problematic fonts, missing text, photos that do not display correctly.The error message does not necessarily mean, that the AppStore could not be contacted.

See: Preview a print project in Photos or iPhoto to avoid issues - Apple Support

And check, if any firewall or other security software like a VPN could be blocking the communication with the Print Products Store.

I keep getting this: There was a problem connecting to the store. Place your order later.

I have tried 6 times.

You are using Photos and not iPhoto, right?

Right

I'm not trying to order a book but individual photos. Does that make a difference?

There is no PDF preview for prints, but make sure, that no VPN or other securiry software can block the connection to the print products store.