Ever since ~10am pacific time today, Try hasn't been scheduling unit test runs, except on B2G. See e.g. https://tbpl.mozilla.org/?tree=Try&rev=f7bb5c8f0683 , which has try: -b do -p all -u marionette,mochitests -t none and which got builds on all platforms, but only ended up with mochitests running on B2G.

(This bug is holding Try closed, BTW. When this is fixed, we should re-open it.)

Assigning to coop (who's on build duty, IIUC); coop, can you take this or suggest someone who can? (Or, do you know of anything else happening on other bugs that you'd expect to fix this?)

jhopkins backed out bug 911946 at about 1340 Pacific. Compile jobs which started after then should schedule tests properly.