where can I recover the data of a deleted sensor ?

That history is gone for good I'm afraid. Do you have a backup of your monitoring database? Then you could use configuration backups and restore the database files from the backup. Otherwise, the data is gone :(

ok :( thank you for your quick answer could you please explain me where can be the backup and how to do it ? thank you

Thank you very much!!!

I found the Monitoring Database and configuration Auto-Backups!!! please explain me step by step how to bacup the database

Thanks

Of course, aside from using a backup solution, you could simply copy the files to another drive or folder from time to time or with a scheduled task and a robocopy script. For example this line:

Stop-Service PRTGProbeService
robocopy "C:\ProgramData\Paessler\PRTG Network Monitor\Monitoring Database" "D:\PRTGBackup\Database\ /E /ZB /COPYALL /X /LOG+:"D:\PRTGBackup\db.log"
Start-Service PRTGProbeService

Note that the probes will continue to monitor their sensors for a few minutes and will deliver monitoring results to the core as soon as it is back online. But alerting will not be available during this period.

This is only a small example and there is no guarantee that it will work for you. Just as a starting point :)

Thank you so much !

You're welcome :)