Apple ID not Supported?

You will have to continue to work with Apple. As started already, make sure you have the correct Apple ID/email address for the account.

If you cannot regain access to the account, you may be able to still use your devices. Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Check the requirements and steps at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” Apple may typically require the original receipt* issued by Apple or an Apple Authorized Reseller. If Apple resets the device this will give you access to the device but won't restore access to the account used to lock it. There is nothing that can be done to expedite an Activation Lock request.

*Apple recommends you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support

Sounds frustrating! If Apple says the ID is “not valid or not supported,” it might mean it’s been disabled or deleted. Double-check the email is correct. If support couldn’t help, try account recovery at iforgot.apple.com. You might need proof of purchase for the phone to escalate with Apple.

If Apple support couldn't help you I am afraid that we as apple users on this mainly user to user forums also cannot help you... I am very sorry for that

This is exclusively a user to user forum. The only time I have sen Apple post in the past year has been when there was a physical safety concern.