Hi, thanks for giving the plugin a try. How many photos are in the album? Are they all public and shared?
I think your Google album is not shared completely or correctly? In your Google Album, under Options, do you have “Link sharing” turned on?
When I view your album on google, I only see one photo (the one that shows on your website). And looking at the source code of your google album, I also see only that one the photo listed in the source. So if there are other photos in your album, they are not being shared, or there is another sharing URL that should be used. If that is the only photo that is in your album, then it might be a bug in the plugin showing the “Google Photo” text.
As you can see in my example Google album, anyone should be able to see all the photos:
https://photos.google.com/share/AF1QipOTJR26-1wnAvB5JloFRq9NHmU16t1ftutJZCbTM0FWSrYqYX05pTt4P0aR84Risg?key=VExMemZVQ0FWU295UEROWXExVlFOQXJjbHpGVktR
And as you can see on my WordPress site running 6.1.1, the plugin works correctly if the sharing is set up.
https://josheli.com/knob/2017/11/21/simple-google-photos-a-wordpress-plugin/