The first thing to do is to figure out the best orientation to READ your tag as this is usually the issue. Download TagInfo or NFC Tools. Both will read an “empty” tag. Do not attempt to write to the tag yet. Use the app to figure out how your phone best reads the tag, The best coupling happens when the tag is perpendicular to the antenna in your phone. Since you cant see the phone’s antenna, this will take a little trial and error but typically the antenna is a rectangular perimeter somewhere on the back of the phone… What phone are you using? Typically the best orientation will be one in which the implant points towards the center of the phone, but from where on the phone is the question. This is where having a DT xLED comes in really handy.
Next go here and click the “Securing your xNT” towards the bottom.
https://dangerousthings.com/shop/xnti/
Use the DT app to secure your tag. Use the orientation you found reads best when writing. Do not attempt to write your tag until you have done this.
Also read the “Practical read range” section.