Mirador viewer

SyntaxError: Unexpected token '<', "<!DOCTYPE "... is not valid JSON

{
  "manifest": {
    "error": "SyntaxError: Unexpected token '<', \"<!DOCTYPE \"... is not valid JSON",
    "id": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1048/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-0ef73d8b-748c-4bcb-8673-c36352ebfe02",
      "cw-a5a9f13c-09fc-48df-92a0-fe4ac7b27a17"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-04566a78-f5cd-42c0-8592-ed54cdb5f81a",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1048/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-a5a9f13c-09fc-48df-92a0-fe4ac7b27a17"
  }
}