Are you saying that you followed the instructions for manually installing TT-RSS 1.5 on that site? Then it is not improbable that things failed with a much newer version; TT-RSS 1.5 is 3 years old. The site explicitly says that the Debian packages are the way to go for simplicity if you have the choice.
If you are running Debian Stable and the packages are not available in the repositories for that Debian version, try to install them manually. You can either drag in packages from other Debian versions via some APT work, or you can just try downloading the .deb package from the Debian package repository online and manually try to jam it in with `dpkg`.
If you want to run newer versions of TT-RSS from trunk: follow regular installation instructions.EDIT:
Also, you are not supposed to visit `update.php` like that, and the guide does not tell you to do that either from what I can see. Read an "official" guide instead if you're stuck.