Selecting multiple accounts to post

"From the post editor, choose which social media channels you would like to post to by selecting the Select Channels button on the top left corner. For example, you may choose just Facebook, or Facebook + Twitter"

https://helpx.adobe.com/express/using/how-to-get-started-with-content-scheduler.html#setupconnect

Selecting multiple accounts to post (1x Pinterest + 1x Twitter) doesn't work for me. What could be the reason for this?