There is a specialized test ongoing in Sisi right now for a different launcher in support of playtesting the new native mac client. You can find more info here:
Native Mac Client Playtest - General Feedback
Native Mac Client Playtest - Known Issues
You’ll need to make sure you have the absolute latest launcher version to connect to Sisi right now.
If you are using a Mac, you must be on MacOS 10.15 or higher (Catalina or Big Sur) to connect to Sisi during this week-long test phase. At the end of the test phase, the launcher will go back to allowing all supported MacOS versions to connect via Wine as usual.