Move user from First Storage Group to Second Storage Group

I am hosting two companies email accounts. All of mailboxes are located in the First Storage Group. I created a new Storage Group “Second Storage Group” and a new Mailbox Database. I tried to move one user to the new storage group and database and I receive the following error:
Logon Failure on database “First Storage Group\Mailbox Database” – Windows account NT AUTHORITY\SYSTEM; mailbox /o=360inAction/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=Cristina.
Error: 1144
Client Machine: 360SVR002
Client Process: Microsoft.Exchange.Search.ExSearch.exe
Client ProcessId: 0
Client ApplicationId: Client=CI

Can anyone please help me with this.