uB disabled in FF Developer

[silat]

As of right now uB is disabled by FF in Dev. 430a2

[luxoflux]

You didn't even mention which uBlock version you're using.

Anyway, either install the signed uBlock here, or disable the signature requirement:

1. Go to about:config
2. Search for xpinstall.signatures.required and double click that (set to false)

(FYI: You won't be able to disable this "feature" in future versions of Firefox.)

[gorhill]

uBlock Origin is signed, install from AMO. You can also install a dev version from AMO if you want the latest dev build.