When transferring Joomla Virtuemart software between servers, the Safe Path location listed in the Virtuemart configuration does not automatically update. Because of this, you see an error 'vmError: Warning, the Safe Path is not accessible (does not exist or no permission).'
The Safe Path is a location Virtuemart uses to store the PDF invoices and delivery notes it generates. Ideally you create this below the root of your website and provide the server path to that folder in the configuration, often it looks like '/var/www/vhosts/mywebsite/safepathfolderhere'. In many cases, shared hosting does not allow access below the root so Virtuemart suggests using a randomized folder name places above the root, below the administrator area, because that has a little extra security generally. In these cases the path looks something like:
You simply add your version of that to the Virtuemart configuration at Virtuemart > Configuration > Configuration > Templates (Tab) > Media Files Settings (Area) > Safe Path. Permissions should be 755.