Thanks for reporting this situation, a quick test allowed me to reproduce the situation, however, based on reading through theirs docs this might require a bit more than just switching endpoints to v2. In particular, the recommended user identifier is now different so any changes to the connections needs to take under consideration if there are already existing users. I’ll try to find additional information about this and will get back to you when I have it.
@kenji a preliminary fix has been made available (I say preliminary) because at this stage it has not yet been deployed to all environment. However, if your tenant is using the US Preview environment then the situation should be resolved. If you are in that situation and can confirm if the situation is addressed that would be great.
Providing a summary of the information in the comments as an answer for higher visibility.
The situation was reproduced and, at the time this answer was provided, it should be already addressed for any tenant in a Preview environment (check support center to be sure which environment your tenant is located). In addition, the fix will follow the normal deployment and reach remaining environments so the situation will be addressed across the board soon.