I am seeing the same error, as well.
I tried the same steps as Hendrik, removing my keys, killing all instances of the extension, readding them, to no avail.
Additionally, I (temporarily) switched back to "tab" mode (from "window" mode), and watched the JS console (set to verbose) and network tab while attempting connection(s), and did not see any pertinent information as to what's occurring to cause the error.
Looking forward to a fix, as I use SSH on my Chromebook daily.
Thanks for the awesome work, chromium team!
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Gerad Munsch