If all the select options in the FuzeDrive utility are grayed out or inaccessible, first try floating your mouse cursor over the button to see if there are any useful tips as to why this may be occuring.
The inability to select usually means there are no available blank drives that the utility can fuze with the operating disk. For example, your system may have a C: on the HDD and a D: on the SSD but no other drives. As there is data on both drives, there is no way to combine the drives without first migrating data off the drive with the D: volume on it.
The possible remedies in this case are:
1. Add a new blank SSD (if HDD is the boot drive) or HDD (if SSD is the boot drive) if you need to retain the existing file systems.
or
2. Backup the data on the non-boot drive to a separate backup drive (USB, or other), then delete all data off the non-boot drive so it is blank. You can now use the blank drive to fuze with the remaining boot drive, expand the resulting FuzeDrive to increase the capacity of the C: boot drive, and copy/restore the data from the D: to the new larger C:
IMPORTANT NOTE: In the 1.3.0.16470PR and earlier software releases, when adding a SATA SSD to an existing NVMe SSD boot drive, the option to Accelerate My Bootdrive may appear instead of Expand My Bootdrive. If using multiple disks in the system, the disk selection dialog box will appear if Accelerate My Bootdrive is selected. Make sure that the SATA SSD being added is selected as a SLOW drive and NOT a FAST drive to ensure the transform completes successfully.