If you have a Developer license you won’t be able to use or switch to StudioX as per latest update.
Refer this release note:
StudioX capabilities into Studio
You can now create a StudioX Task directly from Studio without having to switch profiles. Simply navigate to the Templates and search for the Task which will enable you to create a StudioX workflow. You can take advantage of Project Notebook and other StudioX capabilities. With this change, you can also consume StudioX templates.
Citizen Developers can continue using StudioX as before, without any changes.
If you want to switch to StudioX, you can change your license from Automation Developer - Named User
to Citizen Developer - Named User
and restart the Studio. You will get StudioX