Getting 404 Not found when trying to install python-pip3. Error persists even after update and upgrade. Any idea?
You seem to be running Raspbian Wheezy. This is seriously outdated and the best solution is to start fresh with the current Raspbian Buster.
The reason you don't get updates is that the Raspbian Wheezy repo has been moved to a different location and may soon be removed/discontinued completely.
/etc/apt/sources.list to access this the repo.