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/1007/manifest.json",
    "isFetching": false
  },
  "window": {
    "collectionIndex": 0,
    "companionAreaOpen": true,
    "companionWindowIds": [
      "cw-9b5435e4-ddb7-4e83-9295-a3e1d7ee437e",
      "cw-3de419f7-77c1-4e69-a6c8-744a7466e22d"
    ],
    "draggingEnabled": true,
    "highlightAllAnnotations": false,
    "id": "window-997905df-5cb0-42ae-9041-99d0eeddeaf1",
    "manifestId": "https://cdm16022.contentdm.oclc.org/iiif/info/mgs/1007/manifest.json",
    "maximized": false,
    "rangeId": null,
    "rotation": null,
    "selectedAnnotations": {},
    "sideBarOpen": false,
    "sideBarPanel": "info",
    "thumbnailNavigationId": "cw-3de419f7-77c1-4e69-a6c8-744a7466e22d"
  }
}