Firefox for Android doesn't autofill saved/synced paswords since installing and uninstalling external password manager
External autofill apps change a certain boolean in the Firefox for Android configuration variables, this "setting" can only set back to the old setting by completely uninstalling and reinstalling Firefox or (better) by changing a variable in: about:config


goto about:config
search for: dom.forms.autocomplete.formautofill
set it back to true
refresh your login window and... fixed!