You have Microsoft Teams Version 1.2.00.8864 (64-bit). It was last updated on 4/15/19.
After creating a new team four days ago, we were still unable to get the email address for the "General" channel. Our team name was "Company/Peerless Shipping API Integration". After changing the name to "Company-Peerless Shipping API Integration" Teams was able to successfully generate the email address for the team.
I tested with another team I created and was able to confirm.
Below are the steps to reproduce the issue.
Steps To Reproduce:
1. Create Team with a backslash in the name e.g. "Test/Slash Bug"
2. Add member(s)
3. Click "General" channel
4. Click the ellipsis at top of the channel and select "Get Email Address"
5. The message "We're still setting up your team. Please try again later" will display
5. The message will persist until you remove the backslash and replace with another character (like a dash)