Mapillary alpha version fails to show anything

[Polarbear-j]

JOSM/1.5 (18173 en_GB) Mac OS X 10.14.6, Java version: 1.8.0_291-b10, Oracle

v2.0.0-alpha.32 shows "Error: Could not load image from tile server", does not show any tracks,
and the console output shows a 404 error followed by a number of tile loads, when I turn on the mapillary layer:

2021-08-27 19:07:47.255 INFO: AbstractTileSourceLayer: estimated visible tiles: 54, estimated cache size: 466
2021-08-27 19:07:47.276 INFO: AbstractTileSourceLayer: estimated visible tiles: 54, estimated cache size: 466
2021-08-27 19:07:47.277 INFO: AbstractTileSourceLayer: estimated visible tiles: 54, estimated cache size: 466
2021-08-27 19:07:47.278 INFO: Allocate for tile source layer: 116 MB of memory. Available: 3,591 MB.
2021-08-27 19:07:47.550 INFO: GET https://josm.openstreetmap.de/tested -> HTTP/1.1 200 (120 ms)
2021-08-27 19:07:47.710 INFO: GET https://tiles.mapillary.com/maps/vtp/mly1_computed_public/2/14/8816/5388?access_token=MLY|4223665974375089|d62822dd792b6a823d0794ef26450398 -> HTTP/1.1 200 (422 ms)
(similar GETs follow)

When I click "info" in the layers window, it says:
Mapillary layer: 0 sequences, each containing 0 and 0 images...

(also reported as ​https://github.com/JOSM/Mapillary/issues/189 )