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/1164/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-0b1e5f26-5b34-4b16-8775-a2f0233789d0",
      "cw-7e82a815-7624-4708-b759-f3b66c708162"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-cfa3ef4d-201e-4b4a-b1b2-e138f41bb560",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1164/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-7e82a815-7624-4708-b759-f3b66c708162"
  }
}