@unregistered436 Hey man… so a few things… the first thing is that the chip inside the xM1+ definitely has a way shittier RF performance than the NTAG216 inside the xNT… so it’s going to be worse right out of the gate. Also, we definitely tested all xM1+ tags before re-releasing them… like 5 times each. Now, the silicon chip inside these things is a shitty knock-off from a shady operator trying to avoid lawsuits from NXP and the like… so it’s kind of an inefficient power hungry bitch… on top of that, chip capacitance has a pretty wide delta which makes getting optimal tuning somewhat hit-and-miss with the antennas we attached those chips to inside the xM1+… however all finished xM1+ tags did pass our tests so if it is slightly out of tune it should not be very far off.
That said, it is possible that the tuning might be just bad enough that, coupled with your salty blood and flesh, the cumulative de-tuning that’s happening is just bad enough to cause serous readability problems for you.
There is one other possibility, which is that the second round of sterilization created thermal cycling that damaged the chip, affected it’s tuning, or otherwise created unforseen issues that caused it to stop working… and there is no way for us to test for this because it’s a 13.56mhz chip inside a big steel needle. It is possible, with the right equipment, to get a read on a 125khz tag inside a needle, but not a 13.56mhz… the skin effect is just too great at that high frequency to overcome.
So, at this point, the best I can ask of you is to take an ACR122U PCB out of the plastic shell housing, mark your hand where the xM1+ is, and place the PCB antenna loop over your xM1+ and submit a picture… and we can go from there. If the thing is truly dead, we will replace or refund it.
@killerkickan … since you were able to get a read with the GoToTags software, we know the chip is functional. The 716 byte value you are seeing is the result of NDEF formatting and sector trailer blocks in each sector “eating up” your 1k space. You can find out more about the Mifare “Classic” 1k memory structure from this spec doc; https://www.nxp.com/docs/en/application-note/AN1304.pdf
As for not getting reads from your other readers and devices, chances are that the chip is not coupling well with those readers. You can attempt to improve coupling by trying different positions and orientations. If you have an xLED-HF you can use that as a tool to find the best location and orientation for each reader and then present your xM1+ in the same location and orientation.