Firstly, we should ask Autodesk why they have released a faulty install to the world? After all we pay enough for the software and Autodesk has been creating installs for decades, so at the very least us customers should be able to expect is that the software can actually be installed properly, or else give us a discount or rental credits or a refund until they get it right! I wouldn't drive a new car off the forecourt if the engine won't start, so why do software developers always think it's OK for us customers to put up with faulty goods? Got to be something in the Sale of Goods Act in the UK about this at the very least.
Anyway, rant over, I've had the same problem with Revit LT 2017 from the Revit LT Suite 2017 product set.
I haven't tried the suggestion on this post yet, but this is the dirty fix I used...
When you install Revit LT a RVT 2017 folder gets created on this path:
C:\ProgramData\Autodesk\RLT 2017
I compared this folder with full Revit, which creates RVT 2017 folder on this path:
C:\ProgramData\Autodesk\RVT 2017
The full Revit, which installed without any issues, has the following folders:
Family Templates
Libraries
Templates
along with a few others.
I did a test by copying these folders from RVT 2017 to RLT 2017.
Now I know I was copying MEP stuff and language specific stuff that Revit LT does not use, but what the heck, I wasn't going to sift through these folders and delete the non Revit LT items for my test.
Anyway, I restarted Revit LT, got the templates error dialog, dismissed this and got into Revit LT and selected R > Options > File Locations.
Then I repointed the Default path for family template files, and in Places repointed the Library and Detail Library paths as appropriate. Quit Revit LT, restarted and it all works now.
Obviously Autodesk will frown on this and tell me I may have missed some stuff Revit LT needs, but it seems OK for now.
So, I'm now waiting for a service pack upgrade/fix from Autodesk that fixes this fault.
Mind you, you won't be able to do this if you don't have full Revit installed on your network somewhere. But then, if you don't have any full Revit seats you are pretty stupid as Revit LT is missing some fundamental things like Worksharing, Massing and Conceptual Design and a few other mission critical functionalities. The only staff using Revit LT in my organisation are senior management. Everyone else has full Revit period.