Hello Patric -
We are not aware of any issues that would prevent the eBay site selection menu from operating correctly, so it is unclear what may be occurring for you. Please note that if you open a saved listing you will not be able to modify the eBay site for that listing once it has been saved as the listing creation page is dynamic and the options there depend on the eBay site selected.
However, if you are having this issue with a brand new listing or a listing where you have opened it via Create Similar, please let us know in a support case the details of what you are experiencing so we can look into it for you.
- Craig