There are many, many suggestions to remedy this issue, usually involving file/folder permissions, copying swf files to additional locations or standing on your head balancing a wet fish on your feet!
In the instances I’ve come across it appears Flash isn’t requesting run permission on the site for some reason (the buttons are programmed in Flash) and so the buttons aren’t showing.
In order to remedy this issue:
- Open Google Chrome and in the address bar type: chrome://settings/content
- Browse down the list and select ‘Flash’
- Alongside ‘Allow’ select ‘Add’ and enter the website domain/address of the Magento install (eg. http://www.example.com or https://www.example.com if SSL)
- A quick refresh on the Magento product admin screen should now show the images and the required buttons