Just to make sure we are on the same page here, - you are able to login to your account, but when you do, you find that there is no option to edit your theme?
If you could send me a screenshot here of what you’re seeing, that would be super helpful! In the meantime, you could look at some local troubleshooting steps to try and resolve this:
Clear the cache and cookies on your Google Chrome browser following these steps here and try to login again.
Login on an alternative device i.e. if you’re using mobile, try to access it on desktop - if it works on the other device, this is an indication that you may need to update the one where it does not work.
Try to reset your internet to see if your issue is a result of a network error.