I’ve just been through almost same ordeal but with the assistance of QNAP support I fixed it.
I experienced for instance that the CloudKey number from the box sticker dodn’t match with my NAS. I found that out by using the description in section 8 in this link:
For me that didn’t help me login though, as a 10sec reset on the NAS came before I figured this out. I was afraid of the 10sec reset as I have never tried recovering the folder structure prior to this incident, but here after doing it … it was not a big deal.
The sequence was like this being able to login:
- Uninstall the present QNAP FinderPro.
- Do a 10sec reset as directed in the sequence 1 trough 5 in the link above.
When the new installed QNAP FinderPro was looking for the NAS it saw it as a new NAS was present and not properly configured. The on-screen instruction started by telling me to install the discs in the right order … assisting med to make a new admin account different form the default … and voila I was inn 
Hope you can use some of my experience.
Cheers