This question already has an answer here:

I'm currently trying out Loki, and it's running quite fine as far as I see. Only real annoyance: Firefox is currently showing a bug. If I open a Filechooser in Firefox, no matter if its for saving a page, uploading a file to a site,etc...nothing can be selected. You can browse all folders, navigate through them, highlight an entry, but the options to select an entry are missing. Literally: there is no OK Button.

Any others experiencing this?

marked as duplicate by Daniel Foré Sep 13 '16 at 18:52

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Workaround:

gsettings set org.gnome.settings-daemon.plugins.xsettings overrides "{'Gtk/DialogsUseHeader':<0>}"

It's fixed and should arrive soon.

Not the answer you're looking for? Browse other questions tagged or ask your own question.