Object machine was deleted by EEM administrator, hopefully only logically. Look for it in Deleted machines folder.
If that fails, get machine object information from your backup and import it to live database.
99.9% chance someone deleted it, so check the recycle bin.
Next, get the machine object (from the machine itself's pre-boot recovery screen), then go look in the actual structure of the database to see what happend. For example if the object ID is 00000045, look in folder sbdata\00000002\00000000 - if you see 00000045.WPE then someone permanently deleted the object and you'll need to retrieve it from a backup. If it's a .RMV, then it's still in the recycle bin and you can simply restore it.
Thanks for advice. There is one problem, i am 100% sure it was not deleted and there is no backup. This machine was a brand new client with an new client configuration set (executable). After encryption its object is not in the database.
Any other suggestions?
Perform maintenance on database. Check groups for orphans.
Orphan or not does not affect the machine's ability to sync - it does not matter if the object is in a group or not, the machine does not care about that.
If the machine is reporting the object as missing, then it IS missing - it's either deleted, or in the recycle bin, or somehow the database has switched to one the machine never registered with.