Ok, after even more button pushing, I think I can safely say that the tool you found is completely broken by the looks of things.
Both myself and Blastoise have attempted to put our respective MPANs and Postcodes in to see if it could pick up our S2 meters - which are definitely communicating just fine - but the tool instantly spat out the "meter not found" error for both of us. We noticed it was returning a result incredibly fast - perhaps
too fast, so we decided to try some tricks.
Chucking in completely impossible combinations yielded some rather interesting results. Unfortunately for us, the tool immediately rejected XM4 5HQ as an invalid postcode (d'oh!), despite the fact that it actually is a valid postcode...
It just has a very special purpose. I guess Citizens Advice don't recognise Santa's Grotto or Reindeerland as being a thing in the UK!
Anyway, playing about with it some more and using examples like an MPAN of "1" - which obviously can't be a valid MPAN as it doesn't match the format at all - and a Postcode of W1A 1AA which is a special case postcode assigned to BBC Broadcasting House, I also got the generic "meter not found error" immediately. This suggests the tool may well be completely dead, as I wouldn't expect it to return a failure in under 0.1 seconds if it was to
actually query DCC properly and wait for a response before coming back to me with an answer. It would have probably also spotted that the MPAN was totally invalid and that the postcode in question does not have any addresses on it that can qualify for a Smart Meter of the type that the tool is designed to search for. Businesses can get Smart Meters, but it's a lot more complicated and runs in a slightly different way. I doubt that a tool designed for personal use would be able to look up a business.
If the tool was properly designed, it would have detected that the MPAN was totally invalid and asked me to enter it again before attempting to look it up, not afterwards - and it probably would have spotted that the two postcodes I mentioned here are special cases that cannot possibly be assigned to a domestic customer. On top of that... I find it rather curious that it correctly boots out any postcode starting with X, since none of those are technically valid for the purposes of energy supplies (they can be valid for other stuff though!), but fails to spot the special cases assigned to high profile organisations. Whoops...
Oh, and it's definitely only booting out those that begin with X - I tried one that starts with BX and it accepted it (but obviously failed to get a result afterwards).
Ultimately, my current opinion is that I can't recommend the use of that Citizens Advice smart meter check tool at this time, since it appears to be broken and non-functional. Maybe it did work fine when it was first created, but for some reason it's no longer working properly. It could be that DCC has terminated the API Key for the tool, it might be that the API changed on the DCC side of things or something else entirely. But whatever the cause, I would advise against relying on the tool at this time, until it gets fixed properly. The most up-to-date information is likely to be available via ECOES (for electricity) or Xoserve (for gas). You can ask your supplier to do a lookup anytime free of charge, but there's no self-service option that can do this.
