To troubleshoot WAL replication issues in PostgreSQL where the primary server generates WAL files but does not push them to the standby server, consider the following steps:

1. Check Connection Settings: Ensure that the primary and standby servers can communicate over the network. Verify the pg_hba.conf file on the primary for appropriate entries allowing connections from the standby.
2. Review Configuration Files: Verify the postgresql.conf settings on the primary server, especially wal_level, max_wal_senders, archive_mode, and archive_command. Ensure they are correctly set for replication.
3. Examine Logs: Check the PostgreSQL logs on both the primary and standby servers for any error messages or warnings related to replication.
4. Verify Replication Slots: On the primary, check for the existence and status of replication slots using SELECT * FROM pg_replication_slots;. Ensure that the slot for the standby server is active.
5. Check Network and Firewall: Ensure no network issues or firewalls are blocking the replication traffic between the primary and standby servers.
6. Review WAL Sender Status: On the primary, use SELECT * FROM pg_stat_replication; to check the status of WAL sender processes.
7. Disk Space: Check for sufficient disk space on both servers, as space issues can disrupt replication.
8. Standby Settings: On the standby, ensure that recovery.conf (or standby.signal and postgresql.conf in newer versions) has correct settings for primary_conninfo and restore_command.

If these steps don't resolve the issue, consider more detailed diagnostics, possibly involving network tracing tools or contact support@minervadb.com