If you already have an email confirming the admin access removal, that’s actually useful. Google Ads support usually won’t act unless the request goes through the correct ownership verification flow.
What has worked for some people is reopening the case and clearly stating that you’re requesting account ownership verification, not general access restoration. Attach the original email, any billing proof (old invoices, payment methods), and the account ID in one message.
If standard support keeps looping, using the Google Ads support form specifically for account access issues and asking for escalation sometimes helps, but it can take multiple attempts. Unfortunately, there isn’t a quick fix once admin rights are removed.