localhost:8080/since/0 has no decodable json

[caver456]

211330 [caltopo_python:270:INFO] Opening a CaltopoSession object with no associated map.  Use .openMap(<mapID>) later to associate a map with this session.
211330 [caltopo_python:394:INFO] Opening map G8TEQHH...
211330 [caltopo_python:404:INFO] Initial cache population begins.
211330 [caltopo_python:1034:INFO] inside doSync
211330 [caltopo_python:1708:INFO] -- BLOCKING (sending now, timeout=10) GET http://localhost:8080/since/0
211330 [caltopo_python:2125:ERROR] sendRequest: response had no decodable json:<Response [200]>
211330 [caltopo_python:2126:INFO] f12: clearing syncPause
211330 [caltopo_python:1244:ERROR] Sync returned invalid or no response; sync attempt failed.  Response: False

On caltopo.com that initial request looks like

211937 [caltopo_python:394:INFO] Opening map G8TEQHH...
211937 [caltopo_python:404:INFO] Initial cache population begins.
211937 [caltopo_python:1034:INFO] inside doSync
211937 [caltopo_python:1708:INFO] -- BLOCKING (sending now, timeout=10) GET https://caltopo.com/api/v1/map/G8TEQHH/since/0
211937 [caltopo_python:1080:INFO]   Updating "ids"
211937 [caltopo_python:1087:INFO]   processing 1 feature(s):['5141..']
211937 [caltopo_python:1168:INFO]   Adding to cache:Marker:5141..:MyMarker
211937 [68:INFO] new feature callback called with args ({'geometry': {'coordinates': [-120, 39, 0, 0], 'type': 'Point'}, 'id': '5141781f-59dc-40a4-94ca-4aa435018ac7', 'type': 'Feature', 'properties': {'-updated-by': '11UEE9', 'creator': '11UEE9', '-created-on': 1768679621791, '-updated-on': 1768679621791, 'description': '', 'title': 'MyMarker', 'marker-size': 1, 'marker-rotation': None, 'marker-symbol': 'point', 'marker-color': '#FF0000', 'marker-visibility': 'visible', 'class': 'Marker', 'updated': 1768679621791, '-created-by': '11UEE9'}},)
211937 [caltopo_python:1262:INFO]  dsx: requestThread is alive: True
211937 [caltopo_python:406:INFO] Initial cache population complete.

So the URL is just not getting built correctly at all.