Your code did not insert the image, only the "New Content" portion.

Sorry about the []. It wasn't in the code I pasted. Probably it got there when editing. For some reason, the mouse clicks are mapped to the wrong location when I'm using the editor. Sometimes I don't see where I've typed. Anyway I took it out.

Works perfectly for me. Don't know why it wouldn't work for you.

I commented out the second line. It's not necessary and may be a distraction. Works either way for me anyway.

As I understand your reply, nothing is written into nb by the last NotebookWrite[], which seems strange. And no error (I suppose).

The actual application is as follows (the token obscured for obvious reasons):

nb = CreateDocument[];
data = {};
offset = 0;
checkins = 
  Import["https://api.foursquare.com/v2/users/self/checkins?limit=250&\
v=20231001&oauth_token=XXXXXXXXXXXXXX", "RawJSON"][["response", 
    "checkins", "items"]];
While[Length[checkins] > 0,
      Do[
   	PrependTo[checkins[[i]], 
    "timestamp" -> FromUnixTime[checkins[[i, "createdAt"]]]];
   	AppendTo[data, checkins[[i]]]
   	, {i, Length[checkins]}
   ];
  offset += 250;
  checkins = 
   Import["https://api.foursquare.com/v2/users/self/checkins?offset=" \
<> ToString[offset] <> "&limit=250&v=20231001&oauth_token=XXXXXXXX", 
     "RawJSON"][["response", "checkins", "items"]];	
  ];
GeoListPlot[Table[
   GeoPosition[{data[[i, "venue", "location", "lat"]], 
     data[[i, "venue", "location", "lng"]]}]
   , {i, Length@data}], 
  GeoBackground -> {"VectorClassic", "StreetMapLabelsOnly"}, 
  ImageSize -> Large] // 
 NotebookWrite[nb, 
   Cell[BoxData[MakeBoxes[#, StandardForm]], "Output"]] &

The code Michael provided works perfectly for me on V14.1