You're probably using old version of Traccar.
We have the latest version on server and smartphones:
2025-10-01 11:08:08 INFO: Operating system name: Linux version: 5.15.0-130-generic architecture: amd64
2025-10-01 11:08:08 INFO: Java runtime name: OpenJDK 64-Bit Server VM vendor: Eclipse Adoptium version: 21.0.7+6-LTS
2025-10-01 11:08:08 INFO: Memory limit heap: 1968mb non-heap: 0mb
2025-10-01 11:08:08 INFO: Character encoding: UTF-8
2025-10-01 11:08:08 INFO: Version: 6.9.1
2025-10-01 11:08:08 INFO: Starting server...
2025-10-01 11:08:09 INFO: Health check enabled with period 480000
That's not the latest, but should work. Where are the logs though?
When using iPhone and Android devices, the speed is not being calculated, remaining at zero in most cases.