The people on this forum are only other users like yourself. This is not official Apple Support. If your account has been designated as invalid by Apple then only Apple can unlock it.
Unless you can get Apple to do something about the account then the only alternative I can advise is you give up on the old account (and everything it contained, but you should have backups you kept of important information), ask Apple to reset the device entirely and start using it with a different account.
Refer to How to remove Activation Lock - Apple Support for the various ways to remove an Activation Lock. If you have the necessary information you can do this yourself, otherwise 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
