I have been having the same issue for the last few weeks on either Chrome or Firefox (both latest versions). Clearing cookies fixes this temporarily but the problem reoccurs when I come back to the website, going incognito is also a workaround, but not ideal obviously.
The following error pops up in the JavaScript console after clicking on “Create game”:
------> seek_graph/connect
ogs.4.2-494-gf572026.min.js:456TypeError: undefined is not a function
at q.n.challenge (ogs.4.2-494-gf572026.min.js:1638)
at ogs.4.2-494-gf572026.min.js:556
at ogs.4.2-494-gf572026.min.js:659
at q.$eval (ogs.4.2-494-gf572026.min.js:481)
at q.$apply (ogs.4.2-494-gf572026.min.js:481)
at HTMLButtonElement. (ogs.4.2-494-gf572026.min.js:659)
at HTMLButtonElement.u.event.dispatch (ogs.4.2-494-gf572026.min.js:272)
at HTMLButtonElement.b.dispatch (ogs.4.2-494-gf572026.min.js:1063)
at HTMLButtonElement.r.handle (ogs.4.2-494-gf572026.min.js:266)
ogs.4.2-494-gf572026.min.js.map:1 GET https://a00ce0086bda2213e89f-570db0116da8eb5fdc3ce95006e46d28.ssl.cf1.rackcdn.com/4.2/ogs.4.2-494-gf572026.min.js.map 404 (Not Found)