RoboSats requires Tor Browser, or I2P.
They have the https://unsafe.robosats.com URL that lets you VIEW the site using the "clearnet" (what you are likely using right now to view this reply), but to actually use RoboSats for a trade, you will need to use the link with the .onion address (access using Tor) or the link for the .i2p address (access via I2P).
Fortunately, Tor browser is available on mobile.
RoboSats is planning a mobile app as well so that it can be used without even having to know what Tor is, similar to how something like ... say, BlueWallet has support for Tor as well, without the user even knowing.