Air tag won’t connect and can’t reset it.

Hi,

bought an AirTag, worked fine for the first week (nothing heavy just in a soft padded bag with some work equipment)

then it stopped finding the location and wouldn’t connect to my phone.

the other 3 from the pack of 4 all work well.

searched on here and found a similar thread that said to try a reset by removing the battery and then pressing until you hear 5 noises.

did this correctly but didn’t get any noises at all.

tried a new battery and still nothing.

wont link to phone.

is it a dud?

bought it online via apple store in a 4 pack so what’s my options?

thanks in advance to you great problem solvers