OK, they responded pretty quickly:
Hi Sayontan,
Thanks for contacting Zenfolio Customer Support. I’m happy to help.
There is no API for the new platform, which is what the Portfolio, PortfolioPlus, and ProSuite plans are on. The users with?username.zenfoliosite.com?sites are on the new platform. Any third party plugin or program you are using or developing is only going to be compatible with the Classic platform at this point in time as that would be the API the plugin or program is referencing.
As a courtesy to you, I’ve gone ahead and marked this case with the feature request so you can be updated if/when we have any updates regarding API access on the new platform.
I apologize for any inconvenience this may cause in the meantime. If you have any other questions or concern – please don’t hesitate to write back in to Customer Support!
Best,
Ryan (He/Him) | Customer Support
So, unfortunately their API is not compatible with users on their new platform. If you were a Classic user, their API (and hence this plugin) would have worked fine.
If and when they introduce a new version of the API, I will make the changes in Photonic.
Though this doesn’t actually fix your issue, I am marking this resolved, as there is nothing else for me to do here as of now.