I can't export personal certificates on linux

When I try to export my personal certificate, firefox question the path, but when click on save, the window close and nothing is saved.

Don't show any error but the file (pkcs12) is not created.

Please, help me. In Spain all government procedures need the certificate and can not export it to my other computers.

(ubuntu 16.04, x64; firefox 56.0, x64)

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: firefox 56.0+build6-0ubuntu0.16.04.2
ProcVersionSignature: Ubuntu 4.10.0-37.41~16.04.1-generic 4.10.17
Uname: Linux 4.10.0-37-generic x86_64
AddonCompatCheckDisabled: False
ApportVersion: 2.20.1-0ubuntu2.10
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: aitor 4975 F.... pulseaudio
 /dev/snd/controlC2: aitor 4975 F.... pulseaudio
 /dev/snd/controlC0: aitor 4975 F.... pulseaudio
BuildID: 20171003101344
Channel: Unavailable
CurrentDesktop: GNOME
Date: Mon Oct 16 00:46:56 2017
Extensions: extensions.sqlite corrupt or missing
ForcedLayersAccel: False
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
IncompatibleExtensions: Unavailable (corrupt or non-existant compatibility.ini or extensions.sqlite)
InstallationDate: Installed on 2017-09-11 (34 days ago)
InstallationMedia: Ubuntu-GNOME 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
Locales: extensions.sqlite corrupt or missing
Plugins: Shockwave Flash - /usr/lib/flashplugin-installer/libflashplayer.so
PrefSources: prefs.js
ProcEnviron:
 LANGUAGE=es_ES
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=es_ES.UTF-8
 SHELL=/usr/bin/zsh
Profiles: Profile0 (Default) - LastVersion=56.0/20171003101344 (In use)
RfKill:

RunningIncompatibleAddons: False
SourcePackage: firefox
Themes: extensions.sqlite corrupt or missing
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 06/26/2015
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 2603
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: M5A97 R2.0
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: Rev 1.xx
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr2603:bd06/26/2015:svnTobefilledbyO.E.M.:pnTobefilledbyO.E.M.:pvrTobefilledbyO.E.M.:rvnASUSTeKCOMPUTERINC.:rnM5A97R2.0:rvrRev1.xx:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: To be filled by O.E.M.
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: To be filled by O.E.M.