iOS updates generally aim to enhance user experience, boost security, and fix bugs rather than disrupt core features. Airtag issues after updates might stem from underlying, unmentioned factors. Updates won't typically alter personal data but may refine settings or features. Backup before major updates for safety. Review Apple's update details and backup advice for a smooth process.
This seems purely coincidental so please check the Setting on your device. every Airtag is associated with an Apple ID. If you loging with another Apple ID then the Airta may not avaialble to you on your device that uses another Apple ID.

See what each update does: About iOS 17 Updates, About iOS 16 Updates, About iOS 15 Updates, About iOS 14 Updates, About iOS 13 Updates, About iOS 12 Updates, and so on...