Login doesn't work, smart content gone, products gone in DS 4.9
About a month ago I updated DAZ Studio 4.8 to version 4.9. I did the upgrade, because a couple of the freebies I ordered from the shop at the time said they required a new download method that works from inside DS 4.9. {{EDIT: DAZ Connect}}
When I started DS 4.9, the first thing it did was ask me to login to my account. I put in my registered email and password, and got an error. I have tried to login several times since then, but all I ever get is an error. The error does not even display any error text. It says there is an error, but does not say what it is.

Once in DS 4.9, I immediately noticed my smart content was gone. I don't know where it went. It is just gone.

I was able to get something when I unchecked the "Filter By Content" box, but all it was was a bunch of ! symbols that do nothing.

Then I tried to using the Content Library. I usually find most of my content by searching through "Products", but now the products all show ! symbols as well, and no content shows up in the Content Library window.

Does anyone know how to fix this? I used to be able to get at my content, but now I can't.
If there is no way of fixing this, is there a way for me to downgrade back to DS 4.8 and get things working again?

Comments
First...what operating system are you running?
Second, which version of 4.9? (Screenshot of the Help > About screen would be nice)
Windows 7 (I am not going to "upgrade" to Win10, so don't ask.)
DS v 4.9.1.30 Pro Edition 64 bit
I'd never ask anyone to willing update to that fornicating pile of slug droppings...so no worries, there (I'm a little miffed, the last update basically reset all the stuff on my wife's laptop to 'factory' and I just had to go put everything back...again).
And the latest Studio...there were a couple of connecting/cms type problems fixed in this version, so you have those in place already.
Next, question...is the CMS running (if you have Studio open and pull up Task Manager are several instances of PostgreSQL running)?
What about security software?
This has the hallmarks of something actively blocking/preventing Studio from connecting and possibly the CMS from running.
How do I go back to DS 4.8 then?
I don't need DAZ Connect. I just need DS to work.
Unless you have the installer backed up somewhere...you can't.
So I upgraded and ended up with a version of DS that is less functional then its predecessor, and there is no way back to the working one.
Any thoughts on how I can get the products to appear in the content library again?
I had the same problem, I ended up running the content DB manager and DB migration tools. Turned out that the new install was lookinhg for my content in the wrong place, once everything was located it started working fine.
What security/AV/firewall software are you running?
Does your content show up correctly in Content Library > Daz Studio Formats and Content Library > Poser Formats?
If I go into the tree, I can find most (but not all) of my stuff. It's all there.
It just does not show up in Smart Content, Products, or in searches.
Oh yeah. Let's add that to the list.
Searches don't work.
That's pretty much what I had to do. I set up DS4.9 on my new computer and then installed everything with DIM; but a lot of my content wasn't showing up in smart content.
I right clicked on the smart content tab and selected DB maintenance. Then I checked reimport the metadata box
Every time that happens to someone, it usually means the CMS (Content Management Service, it controls the searches and Smart Content and Products views) either isn't working or thinks it hasn't been told where your perfectly functional and complete database files are already existing. That's why you're being asked these questions, this has happened to other people and there are easy ways to fix your system.
Note to others in this thread; how many times does this make that a "latest 4.9" update appears to have mislaid the database files? There has to be a bug somewhere, I've seen way too many posts like this in the last few weeks to be a coincidence.