can't open my account on a second device

You should be able to log into your account on multiple devices.

Maybe you have encountered a temporal situation. I kindly recommend you try again and let us know if the issue persists. You may send us console screenshots while you are getting an error. Here are the related guides;

How to get a console report from most common browsers?

How to Post Screenshots to Our Support Forum?

Please feel free to reach out if you have other questions or need some more help.