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/1103/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-857c41f2-e67e-4ddf-8739-efa6e1e46500",
      "cw-dcf0573e-6744-4373-ac3b-d104e028b190"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-22c12e70-f672-4591-b5d0-9f1591ae704c",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1103/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-dcf0573e-6744-4373-ac3b-d104e028b190"
  }
}