I’ll jump on this bandwaggon. I got a NExT in P0 Left and an xSIID in P0 Right on the same day. It took about a week to get good reads from my NExT and 3 weeks to get good reads from my xSIID. Bodies are weird.
Also, it took me some time and practice to learn how to orient my phone to the best position possible to read either of them reliably.
You will get there! If the KBR1 sees it, you’re in fine shape and just need to wait a while to get good reads from other sources.
I might also point out that iPhones have a significantly more difficult time with implants than most Android phones do. And even within iPhone or Android, different models have widely varying NFC strength. (See Amal’s video for iPhone tip!) So also matters what device you are using to read/write.
I hope you get a lot of satisfaction from your new hardware! 