Hi,
We are getting this error too. We just purchased the Pro version and updated our ACF plugin by following the V4 to V5 instructions.
Our custom field -> field type -> Content -> Image is not recognized, and the “type” column says “Error Field type does not exist”.
When I create a new field and click on the drop down menu for field type, I see under Content heading:
Wysiwyg Editor
oEmbed
Gallery
Image is no longer listed on that drop down menu.
Thanks for any help you can provide!