I allready tried to reinstall the gnome software center.

But I got this error - message:

"Hoppla! Etwas ist schief gegangen: An AppArmor policy prevents this sender from sending this message to this recipient;type="method_call", sender=":- 1.78" (uid=1000 pid=1894 comm="/snap/snap-store/558/usr/bin- snap-store --gapplica" label="snap.snap-store.ubuntu-software (enforce)") interface="org.freedesktop.fwupd" member="GetDevices" error name=(unset)" requested_reply="0" destination=":1.73" (uid=0 pid=2745 comm="/- usr/libexec/fwupd/fwupd "label="unconfined")