There are a couples of things that will need to be fixed or updated:
You’re subscribing to an event called “UbidotsWebhook”, however, according to the webhook action setup in Ubidots, you’re calling an event called “ubidotswebhook”. Can you make sure these 2 match?
We haven’t tested this integration using a Two-Legged Auth (Server) token, instead, we always created non-expiring token using Particle’s CLI as seen in the article below: Events: Particle functions action | Ubidots Help Center
Please follow the step therein, create a new token with those instructions and then try again.
Last but not least, can you confirm if this still not working as expected? I saw the logs of your event and it seems Particle API responded that the webhook activations worked correctly. For example, this the last entry in the logs of your “control” event: