I'm also having issues after updating Firefox. When trying to add metadata from a page with a list of different sources (in my case, a library's database), I can click on the Zotero-Icon in my browser-window, but instead of opening a seperate window, which lets me choose which ones to add, I only see an empty window, while the connector is not adding anything to my Zotero.

In firefoxs addons-manager, the zotero gives me an error:

[JavaScript Error: "Zotero.Translators</this.init@moz-extension://006a1948-cf95-4f9b-9af1-d44d38aa74d1/translators.js:87:20
Zotero.Translators</this.update@moz-extension://006a1948-cf95-4f9b-9af1-d44d38aa74d1/translators.js:253:22
_handleResponse@moz-extension://006a1948-cf95-4f9b-9af1-d44d38aa74d1/repo.js:178:4
_updateFromStandalone/<@moz-extension://006a1948-cf95-4f9b-9af1-d44d38aa74d1/repo.js:141:4
"]

[JavaScript Error: "Promised response from onMessage listener at Zotero.Messaging</this.init@moz-extension://006a1948-cf95-4f9b-9af1-d44d38aa74d1/messaging.js:205:4 went out of scope" {file: "undefined"}]

I'm on Ubuntu, using the latest Zotero-Standalone.
(After opening pdfs in the browser, importing them via the connector works most of the time, although not always, depending on the website)

Hi, I have the same problem on Ubuntu. And yes, once I resize the window the selection options are there and the import works fine.

Just adding a +1 on this. Trying to resize the popup just makes things reappear.