When I select this... I get this... Nothing in my store content preferences is set to exclude any content for any games let alone TSC, this used to work as intended (and up until pretty recently as far as I'm aware). It was the same when i tried the Dovetail Games Routes link, and one other too (can't remember which as I type this now) all the others displayed the results as expected. This happens on both the Steam client and the Web based version of Steam (whether I'm logged in or out).
Exact same screen here. US Locos works. It does show items in my library so can't be that. (Which isn't useful much.)
Have you checked your language? Hade the same problem a week or so ago and I found out that my preferences hade been reset to Swedish only.
Has any one managed to sort this problem yet? I'm only interested in UK stuff but the UK Locos and Pro range keep throwing up this error. I've had this before but it usually clears in a day or so. Tried logging out and back in, and changing preferences but nothing seems to work.
Still broken for me, I'm not sure if it's a Steam issue or a DTG issue, DTG haven't added any input into this thread so we're just left guessing and waiting.
It doesn't work in private browsing either. I wanted to recommend searching for Train Simulator Class, but... However, it should work when you're logged in: The main difference between the two is the language choice. TSC page states it doesn't support my language. Could be specific to the list, it doesn't support English or somesuch. Pro Range is the same indeed. I figured the Class would work because most DLC does have the prefix, and UK classification uses this term (in contrast to continental, where it's Series or built series).
I tied selecting UK Locos and have the same issue, I tried the others and found the same problem with Dovetail Games Routes. The US Locos and German Locos work fine.