Hi JaysinPTH,
Thank you for reaching out Microsoft Community. We're sorry for the inconvenience this may have caused.
When pressing Shift +@ symbol doesn't let you type it in on your Surface Pro 7 with its typecover, the best resolution I can highly suggest is to get a replacement for the keyboard you're currently using. So, feel free to contact support for replacement options.
If this helps, feel free to mark this post as an answer. Otherwise, don't hesitate to respond to this thread if you need further assistance.
Kind Regards,
Crest_Z