This issue is caused by software defect ID 521796, which affects Metalogix Backup for SharePoint version 6.9.0.15.
Here is an example of the errors you will find in the logs:
;�4(�A��4����#Metalogix Backup Management Service��License key not found in the license database.Exception type: Metalogix.Licensing.LicenseServer.InvalidLicenseException
Message: License key not found in the license database.
Source: Metalogix.Licensing
StackTrace:
at Metalogix.Licensing.LicenseServer.Server.ExecuteMethod(String sMethodName, Object[] parameters)
at Metalogix.Licensing.LicenseServer.Server.UpdateLicense(LicenseInfoRequest info)
at Idera.Pointbackup.Service.Management.Licensing.LicenseHelper.ActivateOnline(String licenseKey, String farmId, Int32 serverCount, String productVersion)
at Idera.Pointbackup.Service.Management.Business.Process.ActivateLicenseOnline(String licenseKey, Guid farmId, Int32 serverCount, Version productVersion, PBLicenseInfo currentLicense)
at Idera.Pointbackup.Service.Management.Service.ManagementService.ActivateLicenseOnline(String newLicenseKey)