Overview

You are not able to work with Salesforce Lightning (e. g. pages are unresponsive) and you want to use only Classic mode, but Playbooks is not connecting with Salesforce Classic as you expect it to.
Also, the following error is displayed:

You can't access Lightning Experience
Lightning Experience is enabled for your organization, but not for you. Want to give it a try? Ask your Salesforce admin.

Solution

This might be a result of the Lightning experience being enabled for your user/ organization.
You need to contact your Salesforce Administrator to resolve this issue in one of the following ways:

• Disable Automatic switching to Lightning Experience by going to Lightning Experience Migration Assistant > Setup users and disabling the 'Encourage Users to Stay in Lightning Experience' option.
  
  
• Disable Lightning experience for your user account:
  1. From Salesforce, navigate to Setup > Profiles.
  2. Edit the profile for the user who needs Lightning experience disabled.
  3. Toggle the Lightning Experience User setting off.
     
     
• Turn off Lightning Experience for your organization.