Generating manifests using IIIF Server module and external Cantaloupe image server

We’re trying to create manifests for images that are held on an external Cantaloupe image server, using metadata from items in Omeka S. To start with, is this possible, or can manifests only be generated for items uploaded to Omeka?

Our main problem is that the manifest isn’t generating items for API version 3 images. I’ve set up a test item with a mix of attached media - some uploaded to Omeka, some IIIF v3 images linked from our Cantaloupe server, a IIIF image from the Bodleian library, and a v2 API image from our image server. None of the IIIF v3 images are displaying in Universal Viewer, and the ones from our image server aren’t listed under “items” in the manifest, but under rendering:

“rendering”: [
{
“id”: “http://digitalvoyages.canterbury.ac.nz/omeka-s/s/home/media/1007”,
“type”: “ImageService3”,
“label”: {
“none”: [
“ImageService3”
]
}
},
{
“id”: “http://digitalvoyages.canterbury.ac.nz/omeka-s/s/home/media/1010”,
“type”: “ImageService3”,
“label”: {
“none”: [
“ImageService3”
]
}
}
],

Does anyone have any idea what might be happening here or where to start looking? Here’s a link to the full manifest https://digitalvoyages.canterbury.ac.nz/omeka-s/iiif/985/manifest, plus the item in Omeka: IIIF item test · UC Library Sandbox · UC Library Omeka.

Many thanks,
Donna