After completing an MCS Catalog Update, the VMs in the Catalog are still using the old Image.
Restart all the VMs from within Citrix Studio and confirm that the VMs are now booting from the new Updated Image.
Note:
To verify if VM is booting up using the new image:
1. Go to the "Search" Tab on Citrix Studio
2. Create a search condition "Pending Update" "is" "Yes"
3. All the VMs associated with the old image will appear which are not booting from the new image.