I've been using the UnArchiver for some time now. It's a very decent decompression utility. I had that one pointed out to me over on the DAZ forums when I caught a slew of downloads of updated PC products which evidently had zero-byte files in them. The built-in decompression on the MacOS (of the time. This was a couple of years ago, when I was still running SnowLeopard) couldn't handle those, and they stumped StuffIt Expander as well. The UnArchiver decompressed them without a fuss.
Couldn't handle these, evidently. Although one of the oddities in this whole business is that the first and 2nd file in the set both come down with Zip file icons. The first is a generic .zip icon. But the 2nd was an icon for the UnArchiver (or, more probably, it's companion/parent application, which does compressing). The first eventually opened up as a 100MB file. The 2nd after some fighting, opened up into a file that from its size probably contained the information from the files labeled 01-10. So it now seems quite likely that I did have it all, even if it was in two pieces. But at the time, I wasn't looking at the file sizes, just seeing that I didn't have an obvious way to get into the other nine files.
Yeah, I can see that they wouldn't want one selecting single items from a list of connected files. So greying them out makes a degree of sense. But being able to select the folder they are in, and letting you know that selecting the folder will work would have been helpful. As it stands, there is no clue.
Or, for that matter, having a toggle to change the default from compressing, to decompressing there in the main window, so one can just drop the whole set into the window and have it all decompress. But noooooo. Can't have that.
It will be the end of the week before I find out if they refund my money. If so I'm dumping the whole thing. Otherwise I'll hang onto it, because I paid for it. But I'm not happy. Particularly since the subscription add-on didn't seem to be an option that one could decline