Impossible to create the root directory

<%- if @topic_view.topic.tags.present? %>
<%= t 'js.tagging.tags' %>: <%- @topic_view.topic.tags.each do |t| %> <%= t %> <%- end %>
<% end %>

SilverStripe 4.6
mampstack-7.3.11-0
PHP v7.4.9
Apache/2.4.41

I am new to SilverStripe v4. I have a successful installation, I have not added anything custom yet, but I can not add a new page (just a normal page, not a custom page). I get:

[Emergency] Uncaught League\Flysystem\Exception: Impossible to create the root directory “/Applications/mampstack-7.3.11-0/apache2/htdocs/ss/public/assets/_tinymce”.

I’m wondering if it is some sort of owner/group permissions problem? Any ideas?

Thanks