The discussion revolves around the site_settings.tos_url setting in Discourse, which is supposed to redirect users to an external Terms of Service page. markschmucker initially reported that setting this URL did not work, as the default ToS page was still displayed at /tos. However, maiki was unable to reproduce the issue and suggested a possible cause could be a cached page.
markschmucker clarified that the issue was specific to updated Terms of Service, not the initial signup process, and later discovered that the problem was due to modifying the setting’s text instead of the setting itself. markschmucker apologized for the mistake, realizing that the setting’s description clearly indicates it should be used to provide the full URL of an external ToS document.
Since there is not a way to make users accept the Terms of Service, I need to redirect them to another location. But that doesn’t work either.
I set site_settings.tos_url = https://www.google.com (or any other url- I’ve tried urls both inside and outside the forum). https://forum.example.com/tos still displays the contents of https://forum.example.com/t/terms-of-service/4. Clicking “Edit this page” still takes me to https://forum.example.com/t/terms-of-service/4.
There is a way to add a checkbox to the sign up form, an example is at How to make users to explicitly agree to ToS - #4 by neil, if you are interested in that approach. 
I’m not able to reproduce this bug. When I set the tos_url the /tos redirects to the URL I set (in my case it redirects to https://discourse.org). Were you perhaps looking at page that hadn’t be refreshed, and still linked to the original topic? 
I should have said there is not a way to make users accept updated Terms of Service, after the signup process.
I refreshed, including Shift-F5 and Ctrl-F5, many times, and it always failed on my home computer. But since you said it worked for you, I tried it just now on my work computer and now it works. I’ll try at home again tonight.
I had been changing the text for the setting rather than changing the setting itself:
rather than the setting tos_url.
After all it says “If you have a Terms of Service document hosted elsewhere that you want to use, provide the full URL here.” so that’s my excuse 