Magento 2 import stuck 503 (Service Unavailable)

[carlosgonz1]

I am trying to import some files with CSV on magento 2, when i click check data, it nevers loads. when i click f12 i get

Failed to load resource: the server responded with a status of 503 (Service Unavailable)

magento/admin_[admin]/admin/import/validate/key/[key]/?form_key=[form key]

[fhennessy]

Fixed by changing permissions and made all files and folders group-writable on server

[fhennessy]

Fixed by changing permissions and made all files and folders group-writable on server