Ok, let me try and explain. Your old meter, as fitted by E.On, was an older SMETS1 type meter, These were supplier specific and would have communicated directly with E.On themselves.
You were ported over to E.On Next, but you could have moved to Scottish, OVO, Octopus or anyone else and your meter would have still stopped working.
This is because when the newer, SMETS2 standard was rolled out in around 2019, it used a centralised communications network (DCC) who now handle all meter data on behalf of ALL the energy companies. Older SMETS1 meters are being 'adopted' onto DCC's networks and in many cases this is successful. However some older meters just don't want to play nicely. DCC have a timescale, by the end of this year, to finish migrating oldermeters, and then if any can't be, they will need to be upgraded.
This is not the fault of E.On or E.On Next. It is entirely down to OFGEMs decision to centralise the system and roll out a newer technology.
Yes, unfortunately you have been caught up in the issue, but so have 1.6 million other people. If DCC cannot migrate your meter, you will get a replacement, but only after their program is complete and every attempt possible has been made. Sorry, but that's just the way it is. Blame the Government, blame OFGEM, blame whoever you like but the whole sad state of affairs is really out of E.On Next's control.