I had a server that had the "Microsoft Exchange Writer" missing. When typing the following command from a command prompt all the VSS (Volume Shadow Copy) writers would come up besides the "Microsoft Exchange Writer".
"vssadmin list writers"
This is what the Microsoft Exchange Writer looks like should it come up:
If it does not come up in the list... to enable it navigate to the following registry key:
Modify the "Disable Exchange Writer" registry key to a value of 0.
After this restart the "Exchange Information Store" service.
"vssadmin list writers" should now display the writer correctly.