Hello Gregorio,
The Redo Log is backed up during database start. For log_backup_using_backint = true, the log should be backed up to your backup server.
You can check the following parts (in case log_backup_using_backint = true)
1. The connection to your backup server is OK or not during database start.
2. Check the backint configureation is correct or not
3. Check the backlog, if note 2233763 - [447] backup could not be completed, [110503] Backint cannot execute /usr/sap/<SID>/SYS/global/hdb/opt/hdbbackint, No such file or directory helps or not.
Regards,
Ning