My I pad altimeter msg unable to join network

See the Apple Support article(s) below.

Connect to Wi-Fi on your iPhone, iPad, or iPod touch

Troubleshooting Wi-Fi issues in IOS.    

Some other things you can try. Do you have access to another WiFi network where you can try? That has worked for several people.

Try a restart.

Restart your iPhone, iPad, or iPod touch         

Try a forced restart.

Reset Device.      

If necessary

Hard reset.        

Do a backup and try a factory reset. Then restore from your backup.

Restore to Factory setting.      

Backup - Restore your device from an iCloud or iTunes backup.