Unable to create a backup in Confluence Cloud

@4000000057159dd406e9a164 2016-04-19 05:54:02,113 INFO [http-bio-2010-exec-1] [ondemand.backupmanager.rest.RootResource] runBackup Starting OnDemand backup
@4000000057159dd407221684 2016-04-19 05:54:02,118 INFO [http-bio-2010-exec-1] [atlassian.ondemand.backupmanager.BackupProcessManagerImpl] startBackup Generated task id = 26b2ee67-a86d-4e6d-84f0-686c731868e3
@4000000057159dd40770da94 2016-04-19 05:54:02,123 INFO [http-bio-2010-exec-1] [ondemand.backupmanager.rest.RootResource] runBackup OnDemand backup finished
@4000000057159dd407c718b4 2016-04-19 05:54:02,129 INFO [Long running task: OnDemandBackup] [ondemand.backupmanager.confluence.OnDemandExporter] doInTransaction Preparing for backup
@4000000057159dd40b460644 2016-04-19 05:54:02,188 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Backward compatibility for export: Checking...
@4000000057159dd40b5730cc 2016-04-19 05:54:02,190 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6442: "Migrate over Documentation Theme settings to Custom Page Settings in the default theme" - Ok
@4000000057159dd40b61bfec 2016-04-19 05:54:02,190 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6439: "Reindexes all PersonalInformation objects, creating them for any users that do not have one." - Ok
@4000000057159dd40b673a44 2016-04-19 05:54:02,191 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6430: "Upgrade to build number: 6430" - Ok
@4000000057159dd40b717374 2016-04-19 05:54:02,191 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6424: "Adds missing multi-column unique constraints to the Crowd database tables" - Ok
@4000000057159dd40b7b6e24 2016-04-19 05:54:02,192 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6423: "Cleaning data that violates constraints we want to add in the next migration task" - Ok
@4000000057159dd40b805fc4 2016-04-19 05:54:02,192 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6422: "Upgrade to build number: 6422" - Ok
@4000000057159dd40b8acbbc 2016-04-19 05:54:02,193 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6412: "Delete all FileStore IDs" - Ok
@4000000057159dd40b8f2504 2016-04-19 05:54:02,193 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6406: "Reindex all spaces" - Ok
@4000000057159dd40b936ac4 2016-04-19 05:54:02,193 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6403: "Upgrade to build number: 6403" - Ok
@4000000057159dd40b97376c 2016-04-19 05:54:02,194 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6193: "Rebuild the Confluence favourites index" - Ok
@4000000057159dd40b9af08c 2016-04-19 05:54:02,194 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6193: "Rebuild the Confluence favourites index" - Ok
@4000000057159dd40b9edc74 2016-04-19 05:54:02,194 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6189: "Upgrade to build number: 6189" - Ok
@4000000057159dd40ba9fc1c 2016-04-19 05:54:02,195 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6180: "Adds a multi-column index to content table that speeds up many common queries." - Ok
@4000000057159dd40badad6c 2016-04-19 05:54:02,195 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6175: "Upgrade to build number: 6175" - Ok
@4000000057159dd40bb1f32c 2016-04-19 05:54:02,195 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Build number 6169: "Upgrade to build number: 6169" - Not Ok
@4000000057159dd40bb68324 2016-04-19 05:54:02,196 INFO [Long running task: OnDemandBackup] [atlassian.confluence.upgrade.AbstractUpgradeManager] getExportBuildNumber Backward compatibility for export: "Upgrade to build number: 6169" prevents compatibility before 6169