Slack New Password for Same Email across Different Workspaces

Question:  Do you have to create a new password for the same email across different Slack workspaces?

Answer:  YES.  Slack considers each workspace as being entirely separate for security purposes.  

• You can type in the same password for each workspace that shares your same email, but nothing is tying them all together on the Slack side except the "string" of your email.  
• This means that if you make a mistake or choose different passwords for each workspace, as a user, you have to manage/remember those differences.

Reference:
https://www.reddit.com/r/Slack/comments/6zsqac/question_are_you_supposed_to_use_different_login/