If other Samsung phones can report the location of the tag then it must consider itself ‘lost’. That means it hasn’t connected to either a device running SmartThings under the account that installed the tag, or to a device running SmartThings under the account of a member of the same SmartThings Location that the tag is installed in, for about twenty minutes.
It also suggests your wife’s phone may not have the ‘Offline Finding’ setting enabled.
Bluetooth has to be kept enabled on her phone (UWB is for searching for a lost tag in the vicinity).
If SmartThings is in play it is important to open the tag in the SmartThings Find app for each Location member with a Galaxy to make sure the sharing settings are set correctly.