crphoto8 Loc: Anaheim, California

There may be a bug in Google Photos. I set up an album in Picasa and uploaded it online which means it went to Google Photos. I sent invitations using a link to several people, Most had no problems viewing the images but one invitee got an error message - 404, the album is not on this server. Then I was sent an album by the same method and I too got the same error message. It took awhile to solve but eventually it became clear that if one is logged into Google like in its Gmail feature then the error message appears. I did forward the invitation to another, non-Gmail, e-mail address, logged off Gmail, clicked on the link in the alternate e-mail address and was able to see the images. Same for my invitee, he got the photos through the same procedure.
So it seems that Google has a bug in its Photos application but there's a way around it.

JD750 Loc: SoCal

Interesting. I suggest you report it to google. I'm sure Google has a feedback link or forum where you can report this. Maybe they will fix the problem.