Updated from 4.0 to 4.9 and having problems

I haven't been using my Daz studio as much as when i first got it a few years ago. I was playing with it and decided to go online and see if I could update it and got the 4.9 Upgrade. It started running the istallation managed and and is redownloading and installing all my content over again. First why is it redownloading everything that is all ready on my computer? one would assume it would only need to download any new content not old content. I am also having a problem with a handful of my content failing to download. Maybe because some stuff is from Renderosity? I can't remember what content came from where but i do know that the majority of my content i bought at the Daz store. Like my Genesis 2 packs are failing.
Comments
I'm not an expert but I think some products have changed, which may trigger a fresh download; again I'm not sure. Or maybe the installation manager ("DIM" -- which has also changed recently eg. April or May, I forget exactly when) just wants the latest "automated installation" files to go along with the new approach(es) to content management. And there may have been the odd bug fix here and there, done to some older products.
Vaguely related: there are "upgrades" or "add-ons" for some things... for instance "The Library" has a set of Iray lights and/or materials.
Not sure what this means. Again **I think** some or all of the Genesis add-ons have had changes done to them over the last couple of years and 4.8 definitely had new Genesis content.