@Cannonz The ER605 isnt making a PPPoE connection. Either you don't have the correct PPPoE credentials configuration or possibly your ISP has 'locked' the connection to the previous routers MAC...

@ashleyh The Growatt Data Logger is still attached to the Archer A8 Wifi, but it will not connect over the internet to the Growatt servers Have you tried disconnecting and reconnecting the data...

@lionelgi All 8 cores are required to give a 1000Mb connection, if one has a bad connection or break then it will often successfully negotiate down to 100Mb and work.

@lionelgi Have you tested the cable used for that connection ? or tried a different cable ?

@Kenkoo Have a look at this thread https://community.tp-link.com/en/smart-home/forum/topic/682450?sortDir=ASC&page=1

@DarrenL Would one to one NAT also apply to the outgoing traffic? My understanding is , yes.