If you are trying to connect a new Instagram account to your Social Media Calendar but it isn't showing after selecting, follow these steps:
1-Go to the Facebook profile that is admin of the Facebook Page linked to the Instagram Business account.
2- Click on the Profile avatar on the top right corner of the screen
3- Click on Setting and Privacy
4- Click on Settings
5- On the left side menu, select Business Integrations
6- On the Simplified app integration, click on View and Edit
7- Select all the Facebook Pages and Instagram Business accounts, then click Save
Now, go back to Simplified and try connecting your account again!