sys.dm_tran_version_store_space_usage reports always zero space used
Azure SQL Database uses Accelerated Database Recovery, and so RCSI doesn't use TempDb for the version store.  Instead the version store is inside the database to enable &quot;Instantaneous transaction rollback&quot;, which is especially important during a failover:

The persisted version store is a database engine mechanism for persisting the row versions generated in the database itself instead of the traditional tempdb version store. PVS enables resource isolation and improves availability of readable secondaries.

Accelerated Database Recovery
So you should look in sys.dm_tran_persistent_version_store_stats, or see generally Manage accelerated database recovery