Trying to read oil level using Apollo ultrasonic sensor

I’m trying to read my oil level into HA. I have an SDR dongle (which works when plugged into a PC), plugged into my RPi, Mosquitto shows this:

2024-03-29 08:53:24: Saving in-memory database to /data//mosquitto.db.
2024-03-29 09:23:25: Saving in-memory database to /data//mosquitto.db.
2024-03-29 09:53:26: Saving in-memory database to /data//mosquitto.db.
2024-03-29 10:23:27: Saving in-memory database to /data//mosquitto.db.
2024-03-29 10:53:28: Saving in-memory database to /data//mosquitto.db.
2024-03-29 10:54:51: Client rtl_433-4801ffffa2cf closed its connection.
2024-03-29 10:54:53: New connection from 172.30.33.6:52426 on port 1883.
2024-03-29 10:54:53: New client connected from 172.30.33.6:52426 as rtl_433-78cfffffa2cf (p2, c0, k60, u'addons').
2024-03-29 11:15:46: New connection from 172.30.32.2:60514 on port 1883.
2024-03-29 11:15:46: Client <unknown> closed its connection.
2024-03-29 11:17:46: New connection from 172.30.32.2:55300 on port 1883.
2024-03-29 11:17:46: Client <unknown> closed its connection.
2024-03-29 11:19:46: New connection from 172.30.32.2:52630 on port 1883.
2024-03-29 11:19:46: Client <unknown> closed its connection.
2024-03-29 11:21:46: New connection from 172.30.32.2:48064 on port 1883.
2024-03-29 11:21:46: Client <unknown> closed its connection.
2024-03-29 11:23:29: Saving in-memory database to /data//mosquitto.db.
2024-03-29 11:23:46: New connection from 172.30.32.2:39856 on port 1883.
2024-03-29 11:23:46: Client <unknown> closed its connection.
2024-03-29 11:25:46: New connection from 172.30.32.2:57156 on port 1883.
2024-03-29 11:25:46: Client <unknown> closed its connection.
2024-03-29 11:27:46: New connection from 172.30.32.2:54994 on port 1883.
2024-03-29 11:27:46: Client <unknown> closed its connection.
2024-03-29 11:29:46: New connection from 172.30.32.2:57490 on port 1883.
2024-03-29 11:29:46: Client <unknown> closed its connection.
2024-03-29 11:31:46: New connection from 172.30.32.2:55104 on port 1883.
2024-03-29 11:31:46: Client <unknown> closed its connection.
2024-03-29 11:33:46: New connection from 172.30.32.2:37232 on port 1883.
2024-03-29 11:33:46: Client <unknown> closed its connection.#

Why might it be disconnecting immediately? How do I investigate what’s going wrong?

Thank you - Rowan