I tried to create/save a new segment for a group but it gave me an error:
Hi @Anna_Li 
welcome to our community.
I reproduced your issue and i confirm it’s a bug.
To bypass this issue now, you must create your first segment directly on the segment settings tab, from
/data/users/settings/segments.
I create a bug report to our team.
Thank again for your feedback.
thank you @Arnaud_Moncel i followed your instructions and created the segment (called CMI) but it’s not showing on the menu tab? how long does it take to show a newly created segment or is this another bug?
It’s pretty strange i see your segment configuration on our database.
Have you got any error logs on your browser?
Hello @Anna_Li
We have released a new version to fix this issue.
You should be able to create a segment from a filter as of now.
If you encounter any issue creating a segment from filters, please do not hesitate to post a new message in this thread.
Sorry for the inconvenience, and thanks for pointing this issue out 
Steve.