That might literally be the problem, especially if you are scripting or reporting then.
A backup log only goes as far as the backup itself. To look for problems elsewhere,
you can see if the live log at About → Show log → Live → Warning gives anything.
30. tra. 2023 9:25: Failed to send message: System.Net.WebException: The remote server returned an error: (405) Method Not Allowed.
{"ClassName":"System.Net.WebException","Message":"The remote server returned an error: (405) Method Not Allowed.","Data":null,"InnerException":null,"HelpURL":null,"StackTraceString":" at Duplicati.Library.Modules.Builtin.SendHttpMessage.SendMessage(String subject, String body)\r\n at Duplicati.Library.Modules.Builtin.ReportHelper.OnFinish(Object result)","RemoteStackTraceString":null,"RemoteStackIndex":0,"ExceptionMethod":"8\nSendMessage\nDuplicati.Library.Modules.Builtin, Version=2.0.6.3, Culture=neutral, PublicKeyToken=null\nDuplicati.Library.Modules.Builtin.SendHttpMessage\nVoid SendMessage(System.String, System.String)","HResult":-2146233079,"Source":"Duplicati.Library.Modules.Builtin","WatsonBuckets":null}
30. tra. 2023 9:25: HTTP Response: 405 - Method Not Allowed: 405 Method Not Allowed The method POST is not allowed for this resource.
{"ClassName":"System.Net.WebException","Message":"The remote server returned an error: (405) Method Not Allowed.","Data":null,"InnerException":null,"HelpURL":null,"StackTraceString":" at Duplicati.Library.Modules.Builtin.SendHttpMessage.SendMessage(String subject, String body)\r\n at Duplicati.Library.Modules.Builtin.ReportHelper.OnFinish(Object result)","RemoteStackTraceString":null,"RemoteStackIndex":0,"ExceptionMethod":"8\nSendMessage\nDuplicati.Library.Modules.Builtin, Version=2.0.6.3, Culture=neutral, PublicKeyToken=null\nDuplicati.Library.Modules.Builtin.SendHttpMessage\nVoid SendMessage(System.String, System.String)","HResult":-2146233079,"Source":"Duplicati.Library.Modules.Builtin","WatsonBuckets":null}