The range of an NFC tag is only a few centimeters (2 cm on average).
To properly read an NFC tag, it is necessary to bring your smartphone close to the tag, or even place the tag on it.
It is important to correctly place the NFC tag on your reader during the entire reading or writing procedure. If you move your tag during the process, errors may occur. If so, you need to try again.
Generally, the NFC chip of your smartphone is placed on the back of the device, at the top or in the middle. And for some devices, the chip is located in the battery.
It can happen that when you change your phone battery, you end up with a counterfeit battery that does not contain an NFC antenna. Thus, a smartphone that was NFC compatible is no longer compatible. Pay close attention to this when changing your phone battery. Always use official batteries.
If you have a case on your smartphone, it may be blocking the signal and prevent NFC reading/writing.
If you are still having problems scanning your NFC tag, you can go to this page for more information: https://www.wakdev.com/en/apps/nfc-tools-android/support.html