This error appears when the "/tree.json" file is missing from the server or the server isn't configured properly.

First try to Upload the album again. (No need to "Upload All", just the plain "Upload".) If a little triangle appears in the lower right corner try to Upload again.

If the upload had succeed, check the album in the browser with "force refresh" (Ctrl-F5 in Chrome), to get rid the old files.

If the same error remains, open this page and enter the link to tree.json on your album's top level page, e.g.: "http://mysite.com/album/albumName/tree.json"

If the server is "Microsoft IIS" or "Microsoft Azure", the easiest way of getting rid of this problem permanently is by adding JSON to your server's allowed types. (Provided you have access to server settings.)

1. Open IIS Manager
2. Display properties for the IIS Server
3. Click MIME Types and then add the JSON extension:

• File name extension: .json
• MIME type: application/json

4. Go back to the properties for IIS Server

• Click on Handler Mappings
• Add a script map
• Request path: *.json
• Executable: C:\WINDOWS\system32\inetsrv\asp.dll
• Name: JSON

If you don't have access to server settings, you might want to ask your service provider to allow JSON files on their server. If they refuse it, probably it's better moving on, and choosing a decent hosting company, preferably with Linux/Apache hosting.

You can also turn ON "Settings / Tiger / Site / Site admin / Use Microsoft IIS or Azure server configuration", by which TIger will add a file called "web.config" to the album, which allows JSON files in the album's folder only.

If the server was "Apache/Linux" already, that means the file is still missing, or the server is rather old, or poorly configured. You might want to ask your hosting provider to update the server software and/or allow JSON files.