uBlock no longer works with SeaMonkey 2.52

uBlock 1.11.4 does no longer work with unzipped installer of official en-US SeaMonkey 2.52a1 (NT 6.1; WOW64; rv:55.0) Gecko/20100101 Firefox/55.0 Build 20170406002917 (Default Classic Theme) on German WIN7 64bit. add-On looks active in Add-Ons Manager, but Icon is missing in Navigation bar and can’t be added.

Still worked fine with unzipped installer of unofficial (by FRG) en-US SeaMonkey 2.52a1 (NT 6.1; WOW64; rv:55.0) Gecko/20100101 Firefox/55.0 Build 20170326124008 (Default Classic Theme) on German WIN7 64bit. After having used Build 20170406002917 I can restore the uBlock Icon in the Navigation Bar, and uBlock will work fine.

And since yesterday afternoon uBlock 1.11.4 has become working again with Build 20170406002917. I haven’t a clue …