For those of you using MS' Edge or Google's Chrome the problem is likely due to new versions (both v84) of the browsers being released recently that have disabled TLS 1.0 by default. As RootsChat is still using TLS 1.0 it results in the browser blocking access to the site.
No doubt RootsChat will be updated in the near future but in the meantime you can re-enable TLS 1.0 in your browsers. It's not ideal, as TLS 1.0 isn't secure, and changing the browser settings will apply to all websites that use TLS 1.0 (which shouldn't be many).
If you do re-enable TLS 1.0, I'd suggest reverting the change once RootsChat switch to a newer version, to avoid any possible security issues.
Changing Edge (desktop) settings:1) Open a new tab
2) Open the settings by entering the following in the address bar: edge://flags
3) Enter TLS in the search field
4) Locate the "Enforce deprecation of legacy TLS versions" setting
5) Change the setting, in the drop list, from 'Default' to 'Disabled'
6) After changing the setting a 'Restart' button will be displayed, click it to restart the browser for the change to take affect.
After changing the setting you should be able to access RootsChat.
See attached for example of the settings.
Note that there are 2 versions of MS' Edge web browser, the older one is referred to by MS as Edge Legacy (aka EdgeHTML) and the newer one as simply Edge (aka Edge Chromium). MS have been pushing out the newer version via the Windows Update process so most people will likely have it already. The simplest way to tell what version you have is by the logo, if it has the blue 'e', it's the old version and if it has the swirly blue & green logo, it's the new version.
The steps above are for the new version of Edge. If you are still using the old version you can opt to install the new version by downloading it from MS.
Microsoft > Download New Microsoft Edge Browser
https://www.microsoft.com/en-us/edgeArticle with some information about the new Edge:
HowToGeek > What You Need to Know About the New Microsoft Edge Browser
https://www.howtogeek.com/659857/what-you-need-to-know-about-the-new-microsoft-edge-browser/Changing Chrome (desktop) settings:As per changing the settings in Edge but in step 2 enter the following in the address bar: chrome://flags
(Note, I don't have a machine with Chrome installed to test with but as Chrome and Edge (new) use a common code base, it should be very similar).