Welcome to the Shopify Community! I'm Ash, and I work at Shopify.
I understand you're currently trying to change the EIN associated with your Shopify account, and it sounds like you may have already spoken to our team regrading this change. Do you currently have a support ticket open with our team? If so, I suggest following back up in that ticket for the most direct assistance with making this change for your account.
In order to make any changes to sensitive information or investigate any account-specific issues or queries, we need to ensure we're speaking with an authenticated member of the account or the account owner. Authentication can be preformed via live chat, a phone conversation, or email. If you don't yet have an open support ticket, please head over to our Help Center and follow through the steps to get in touch with the appropriate team. They will be able to help with taking the next steps for changing your EIN.
For anyone else who may be experiencing a similar situation, please do the same and contact our support team through the Help Center so we can further assist.