Opting into the Steam beta program solved this particular issue. Clicking the link in the Steam client now opens a download window. (I do find it odd that such core functionality was broken in a normal release though. When will the current beta become standard, so I can opt out again? I had intentionally stayed out of beta because I prefer a more stable experience to having the latest features.)

it has broken several times, and been fixed

so... not sure why it isnt mentioned in the update logs

Another alternative, you can also open the store page in a regular browser, click the download button, and then allow it work with Steam application.

@arrowgent thanks for the confirmation. @byte1024 actually if you see the referenced issue in the OP, that's exactly what I was trying to do the first time I encountered this error, and it didn't work.

Same here. I noticed it a few times recently after purchasing a new title. I didn't give it much thought because installing from the library screen worked fine.

Today I tried to download a demo for a game, no success so far.

Update: I opted back out of Steam Beta, which reinstalled the Feb 11 2020 non-Beta Steam client, and this issue is gone. I was able to click the download button on https://store.steampowered.com/app/907000/The_Navigator/ within the Steam client, and it popped up a dialogue with a literal %game% in the title, followed almost immediately by the download/install options dialogue, which then worked fine.

This could just be the web code served by the Steam store. It's the same whether you are looking at the page in the Steam client or the store via a browser, and it'll update on it's own cycle independent from the Steam client.

Unless someone currently has this issue still reproductible, we will close.

Unless someone currently has this issue still reproductible, we will close.

I still see the issue. I click the "Download Demo" button on the Factorio store page and nothing happens.

I'm still seeing it too, as I said. 100% reproducible here both on beta and on non-beta.

Interesting point you bring up @TTimo though about web code—and actually I can confirm it's not related to that, because I can, with no Steam web sites open in my browser, open a new tab, type steam://install/452280 in the address bar, hit Enter, and get the same result: my Steam client reverts to the main store page (or opens to it, if it wasn't already running.)

I see a workaround described, by going to the browser and using steam:// links. @codingthat had some problem in #6942 with the steam URL setup on his system that is now fixed.

Now everyone should be seeing the download button working in the steam beta client (even looks like you can go back to stable client afterwards?). If that's correct, then I think we can close.

(also, I do not know the schedule of beta client -> stable promotion .. "soon").

Sorry @TTimo my last message was in error, I was conflating with issue #6942. What I said in the message before that is correct though: opting into beta fixed it, and it stayed fixed when I opted out.

That said, I'm not sure @inguin of your status. Did you try opting into Steam client beta?

I can confirm that changing to beta fixes the issue. Going back to stable makes it return, though.

Fixed in beta.