unable to activate passive database copy

An Active Manager operation failed. Error: The database action failed. Error: Operation failed with message: MapiExceptionTooManyMountedDatabases: Unable to mount database. (hr=0x8004060e, ec=-2147219954) Diagnostic context: Lid: 65256 Lid: 10722 StoreEc: 0x8004060E Lid: 1494 ---- Remote Context Beg ---- Lid: 37952 dwParam: 0x1ED11122 Lid: 35200 dwParam: 0x1F2C Lid: 42480 StoreEc: 0x8004060E Lid: 59632 StoreEc: 0x8004060E Lid: 48432 StoreEc: 0x8004060E Lid: 35408 StoreEc: 0x8004060E Lid: 54336 dwParam: 0x1ED11326 Lid: 35200 dwParam: 0x1F2C Lid: 1750 ---- Remote Context End ---- Lid: 1047 StoreEc: 0x8004060E [Database: DB1onEX1, Server: EX2.bookstop.local]

i ALSO TRIED FROM POWERSHELL : >Move-ActiveMailboxDatabase db1onex1 -ActivateOnServer ex2 -SkipClientExperienceChecks   i RECEIVE THE FOLLOWING ERROR

An Active Manager operation failed. Error: The database action failed. Error: Operation failed with message:
MapiExceptionTooManyMountedDatabases: Unable to mount database. (hr=0x8004060e, ec=-2147219954)
Diagnostic context:
    Lid: 65256
    Lid: 10722   StoreEc: 0x8004060E
    Lid: 1494    ---- Remote Context Beg ----
    Lid: 37952   dwParam: 0x1EBFAEA2
    Lid: 35200   dwParam: 0x1F2C
    Lid: 42480   StoreEc: 0x8004060E
    Lid: 59632   StoreEc: 0x8004060E
    Lid: 48432   StoreEc: 0x8004060E
    Lid: 35408   StoreEc: 0x8004060E
    Lid: 54336   dwParam: 0x1EBFAEE1
    Lid: 35200   dwParam: 0x1F2C
    Lid: 1750    ---- Remote Context End ----
    Lid: 1047    StoreEc: 0x8004060E [Database: DB1onEX1, Server: EX2.bookstop.local]
    + CategoryInfo          : InvalidOperation: (DB1onEX1:ADObjectId) [Move-ActiveMailboxDatabase], AmDbActionWrapperE
   xception
    + FullyQualifiedErrorId : [Server=EX2,RequestId=ac79bea1-91e3-413b-ab84-5b92740f24ad,TimeStamp=8/9/2016 12:20:03 P
   M] [FailureCategory=Cmdlet-AmDbActionWrapperException] DE6E94E,Microsoft.Exchange.Management.SystemConfigurationTa
  sks.MoveActiveMailboxDatabase

Exchange server is standard edition and I only have two active copy on it