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/895/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-10a8eb0c-fcb8-48c1-b50c-6a44b40075a8",
      "cw-09e30ff7-5566-4909-b96a-c6e36b9dd561"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-503999b0-9231-4c83-8220-e219b708104c",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/895/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-09e30ff7-5566-4909-b96a-c6e36b9dd561"
  }
}