Initialization of a NAS with a second-hand HDD might failed due to incompatibility of the partitions created in it. To check the partitions created and to delete them manually you can log in to the NAS using Putty and typing the IP address of the NAS using admin user and its password. After that run the following commands:

[~] # parted /dev/sda print     {sda is the disk in first bay, letters denote the trays/bays; make sure is the correct one}
Warning: /dev/sda contains GPT signatures, indicating that it has a GPT table. {Example of output with a TS-220}
However, it does not have a valid fake msdos partition table, as it should.
Perhaps it was corrupted -- possibly by a program that doesn't understand GPT
partition tables. Or perhaps you deleted the GPT table, and are now using an
msdos partition table. Is this a GPT partition table?
Yes/No? yes
yes
Model: Seagate ST2000NM0033-9ZM (scsi)
Disk /dev/sda: 2000GB
Sector size (logical/physical): 512B/512B

Partition Table: gpt
Number  Start      End        Size         File system       Name                                  Flags                   {Incompatible partitions and structure with QNAP NAS}
1           17.4kB   134MB    134MB                            Microsoft reserved partition   msftres
2           135MB   2000GB   2000GB   ntfs                 Basic data partition

[~] # dd if=/dev/zero of=/dev/sda bs=1M count=1000 {sda is the disk in first bay, if you need to clean other HDDs, confirm the bay and use its label; e.g sdb, sdc, sdd}
1000+0 records in
1000+0 records out
[~] # parted /dev/sda print
Error: /dev/sda: unrecognised disk label       {to check the disk is clear}
[~] # reboot {NAS restart/reboot, wait for a short beep and a second long one; find the NAS with Qfinder}

After this procedure Qfinder should prompt the wizard and initialization shouldn't fail.

Note: applies for firmwares below 4.0.5