The App keeps asking for permission to “Have offline access”, why?

This prompt could come because of two parameters,

• access_type (if it is ‘offline’)
• approval_prompt (if it is ‘force’)

make sure you have set access_type to ‘online’ and apporoval_prompt to ‘auto’

 $client->setAccessType('online');
 $client->setApprovalPrompt('auto') ;