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/893/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-85132ec5-48d1-49d8-9252-f8c5b7b96128",
      "cw-75320875-cada-4f2f-861b-dff3b0286d85"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-17f7e2ae-b173-4a83-99b1-9b852b2510ac",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/893/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-75320875-cada-4f2f-861b-dff3b0286d85"
  }
}