After I changed the battery on Airtag I cant pair with my iphone. Welcome for suggestions. Thank you

Hey there Juan150,

We'd like to help by providing an article that discusses issues with setting up an AirTag with your iPhone, along with listing the steps to take for resolving it under the section 'If you can't set up your AirTag' here: Set up your AirTag using your iPhone, iPad, or iPod touch

If you still have an issue after trying those steps, we recommend letting Apple Support know what's been tried as they'll be in the best position to assist further: Get Support

Cheers!