Why can't I successfully write to tags?

Sadly there are some environmental circumstances that cause issues for some.
These are due to the phone having issues acquiring or maintaining a connection with the tag.
In those instances the phone could still wrongly show a checkmark to indicate success prematurely.

Some solutions that have resolved this issue for most people are:

• Making sure that you’re using high quality tags with big antennas
• Removing any case you might have around your phone
• Some models have an NFC antenna that sends a very narrow signal. So it helps to reposition the tag to your phone’s specific sweet spot, found by trial and error.
• Holding the tag until well after the checkmark. iOS doesn’t communicate any writing process, meaning that the ready to scan animation will repeat itself despite phone writing to the tag in the background. This can take up to 60 seconds.

Since this issue typically means that the writing process got interruped before the tag could be locked, it means that in almost all cases you can reuse the tag and try again with the same tag.
In other words: should you experience this issue, the tag isn't wasted.