Well, that's a lot of frustration in one post.
For the type of evaluation you're asking for, I would resize the photo to a "mere" 1920 pixels wide (or 1280 tall if it's portrait). That way it can be viewed on HD monitors fairly easily, without breaking the server or the network. Also, save as "high quality jpeg". The artifacts from jpeg compression will be mild enough no one will notice.
As for uploading, we'd have to see the error-- which the simple version, you could take a screenshot and upload that, except... you're having problems uploading. So that's an issue. Is there any more detail on the error message?
As for phone images, again, they're just too large-- phones are now capable of producing 50+ megapixel images, and Photrio was never set up for huge image uploads. You can resize those as well, and should be able to upload at a smaller size. Since detail and resolution aren't your concerns (probably), you shouldn't need to upload an original image-- a resized version should be sufficient, as long as it's not teeny-tiny.