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Well, this issue is not caused by Jomsocial, but this is caused by your Joomla template, when I test it with beez3 template the jomsocial toolbar is showing fine.
Please you report this issue to your template "HTTPS Joomla 3 Bootstrap template - Standaard" developer
Have you contacted your template developer? please you compare the Jomsocail with your template and with default Joomla template, with default Joomla template everything is working fine
yoursite.nl/index.php?option=com_community&template=beez5
And regarding group, I just check it and I can enter to detail group as well.