Mac nextcloud client Nextcloud- freezes when trying to accept access

I am running nc und ubuntu 16.04. Its running, version 16.0.0.
I installed client on mac (Nextcloud-
access to server seems to work (no error)
login with user/pw works (no error)
then being asked to accept access to mozilla whatsoever, hangs and freezes does not come back.
I use safari.
upload of screenshot to this question does not work either, tried with cut and paste at last…

thanks for help