Can't request to join a club - Apex

Your alias “Sinon \” could be the issue, it that backslash is part of your name. \ is often used as an escape character and may be causing a parsing error with the text management, causing the whole operation to throw. If it’s convenient for you, editing to it name to remove that \, or escape it by changing it to “\\” might resolve your issue, but it probably won’t.

Still, often is easier to start with the easy changes and see if it fixes, as they can be done more quickly. Also note that if this does work you could then just change the alias back right away and probably not encounter any issues.