Do you mean the Woodhead Route? It should show up if it has downloaded properly. Depending on when you purchased it, of course, it may need time to take some time to properly install. If you look under your DLC list, is the Woodhead box ticked?

its the steam workshop one from sheffield to huddersfield

Ah, if it is a workshop line, then it may take a while to download. Sometimes it is worth leaving the TS page open on the ''drive'' option, as the decrompressing and downloading of files takes a while. A small message should appear saying ''dowloading workshop scenarios.''

Where is it not showing up? Until you acquire scenarios for it it won't appear under the Career or Standard tabs in the drive screen. If it doesn't appear under the Quick Drive tab that's a different matter.

Might be a daft question, but do you have all the requirements needed to allow this route to work, as listed on the Workshop download page.

Woodhead Route.
European Loco & Asset Pack.
London to Faversham High Speed Route.
Donner Pass route.
Test Trak.
Great Western Main line Route.
Riviera Line, Exeter to Paignton.

yes

OK then, it was just a thought.
It may not have fully downloaded. When you subscribe it will show as downloading at the bottom of the Steam page. When that's done, go to TS main menu then Drive, Workshop tabs, it should then fully downlad into TS. Then you shloud be able to find it.

Hope this helps.