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/1185/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-2eca7d14-fdb0-4c90-9a44-8617ebb1f783",
      "cw-df291728-2fb6-4f0a-8e48-c5d9f59aa0cf"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-5dfbd62a-70a6-468e-8c37-952da41370ce",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1185/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-df291728-2fb6-4f0a-8e48-c5d9f59aa0cf"
  }
}