Hello Luis,
Thank you for reaching out to us.
Since I am not sure which specific base are you trying to create and unable to repro your issue, I would like to request more details from your end.
Do you mind sharing the screenshots of
- What base you have selected to create?
- When you click 'Add' what exactly is happening?
- Which region are you trying to select?
Are you choosing any of the base like displayed in the below screenshot? If so, which one is it?

Please provide the requested details, so we can investigate it further.
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Thanks in Advance.