Ah! ok, ok i got it now :) Here: https://docs.opnsense.org/manual/how-tos/cloud_backup.html
it says:
So, if nothing in settings has been changed, backup will not be performed :)
it says:
QuoteAfter set-up, the backup feature will run a first backup of the OPNsense configuration file. Then, if the configuration is subsequently changed, a new backup will be run once per day early in the morning.
So, if nothing in settings has been changed, backup will not be performed :)