Rae from Shopify here. Thanks for posting this question - I'm happy to lend a hand!
To clarify, are you the store owner on your account? If not, it's important to note that these changes can only be made by the store owner. However, if you are the store owner, are you trying to change the name of your store, or your own name within your Shopify admin?
To change the store name, just log in to your store's admin, click on 'Settings > General' and edit the name of your store under 'Store name'.
However, if you're looking to change your own name as the store owner instead, head to 'Settings > Plan and permissions' and click on your name under 'Store owner'. From here, you can click 'View account settings' and edit your first and last name as needed. If you see multiple staff accounts connected to your name under 'Settings > Plan and permissions', then I recommend removing any duplicates by following these steps. This will ensure that you only have a store owner account, and one set of login credentials.
If this doesn't help resolve things, can you tell me a bit more about what you're trying to change, and where you're seeing this error?
Please also reply back to me here with a screenshot of the exact error message you're receiving so I can take a closer look into this. Before posting this screenshot though, it's important to make sure that any of your sensitive, store-specific, or personal details are blocked out from the image to protect your own privacy.
I look forward to hearing back from you and continuing to help out with this!