"PPCStore" is some third-party software, part of "LeopardRebirth", I think.
That's a theme addition for PPC Leopard, most recently to make the system look similar to macOS Sierra, but is not Apple-supported, nor is it a part of Apple's software.
I do have that installed on an eMac, running Leopard, of course.
Tried Apple's Software Update, which checked for software, finding no updates (but it worked)
Also launched my copy of PPCStore, which opened up, showing apps that I could download - so that appears to be working, too.
Is your internet connection working on your PPC Mac? (Can you open Safari, or TenFourFox, and open web pages without any problems? I would suggest a page that would update with today's news, so you know that it is loading a page, and not just showing old information, without actually loading a page)