My QNAP NAS stopped accepting NFS connections last week. I tried a number of things, in collaboration with Perplexity, to re-establish the links. However, during the process I managed to lock myself out of the QNAP web interface.
It is possible to do a soft reset on a QNAP NAS, which preserves data and returns the login to default. As the @techman knows one has to be careful doing this with a QNAP NAS but a three second hold (and one beep) reset the NAS. I needed to set up a DHCP server on that subnet and it finally defaulted to the first address in the lease space.
To reset the login credentials you used to login with admin:admin. This was rightly considered to be too insecure and was changed to admin:${MAC address}. The MAC addresses are displayed on labels pasted to the bottom of the machine. I tried this but it didn’t work.
QNAP also has a QNAP Pro Finder tool that will query the NAS for ip address and MAC address. It did not work under Debian but I managed to get it going on a Macbook Air under the Mac operating system, but I still had no joy in logging in.
Back in linux at the NAS web interface I removed all non hexadecimal characters and converted all letters to upper case. Again this did not work.
The NAS has three NICs so I asked Perplexity if I should try the other NICs. She said this was unusual but had been reported to be successful by some users. I therefore tried all nine combinations of MAC address and NIC interfaces. Failure.
By this time I was feeling somewhat frustrated but I googled the issue and found some links to Reddit. A recent post noted that QNAP had changed their procedure and now used their Cloud key to get access. I gather this enables configuration over the net from a remote site using their remote proxy.
Thankfully I noted that the Cloud key was also displayed on a sticker on the bottom of the NAS and using this got in and re-enabled the logins and security.
This tale of woe is no different to many others in trying to get computers to do what you want. What was different this time was that Perplexity made up the suggestion that trying various NIC / MAC combinations would work. Admittedly I probably contributed to this response by more or less asking that as a direct question.
In retrospect I believe my mistake was in “leading the witness”. This is severely chastised in court on the basis that it will not lead to the truth emerging.
I hope I have learnt my lesson.

