The method iNaturalist has been using to connect to Google Photos via the web on our photo import page is no longer supported by Google so importing photos from Google Photos is currently not functional.
iNaturalist is working on a fix and we hope to have it up and running again soon.
I did a Google Photos import yesterday on the latest version of the Android iNaturalist app - it seemed to work fine. To be clear, the method I used was: Open Google Photos, select all the picture I wanted to share in Google Photos, then ‘shared’ them to iNaturalist.
This is specific to the method used on the web, which was linked to in the post, but not mentioned specifically. I’ve edited to make this more clear, thanks!
My apologies, I clearly misunderstood that.