I am using the NTAG I2C plus chip NT3H2111 together with an antenna I designed myself to establish NFC communication between the tag and my phone. The antenna design is based on your class 5 antenna design guide and a proper capacitor to get resonance. The first antenna I made works perfectly, I can both write to it and read from it with the help from your applications TagInfo and TagWriter. However when I made a second one with the exact same design on the pcb I I am not able to write to the tag anymore, when I am using the TagInfo application and scan the tag I only get the message “NXP IC detected ” and not the one “NFC data set detected” and on the IC info side I do not get the “NFC Forum NDEF-compliant tag” line. This message and line was visible with my first antenna and also when I scan your flex antenna class 5 which I bought for reference. I have tried to change the tag multiple times and also to change the capacitor value but nothing changes. I am able to read the tag but when I try to write I only get “store failed” on the result in TagWriter. It feels like something is wrong with the tag since I am doing nothing different from my first antenna and I have also erased the tag to factory default so there is nothing that should prevent me from writing to it. Do you have any idea of what can be wrong or what has happened with my tags?