Am unable to sign in my iCloud to my new iPhone.

Apple has two related features, Activation Lock ( Activation Lock for iPhone and iPad - Apple Support ) and Find My ( iCloud+ - Find My - Apple ), which are designed to prevent anyone else from using an iPhone, iPad, or iPod touch if it's ever lost or stolen. Deactivation of either requires knowing the Apple ID (email address, or possibly a telephone number in some countries) and password that set the feature, or by placing a special request to Apple to reset the device. This Apple Account information essentially defines the current ownership of the device.

If you do not know the required information, are not the signed-in owner, or do not have Apple accepted proof of purchase, get the owner of the account to remove the lock, or return the device for a refund, or recycle the device. The device is otherwise useless to you. If the owner is unknown and has not provided contact information as a message showing in the login screen, there is no way to contact the owner unless the person who gave you the device knows them.

Here are additional resources if you are the account owner, can find the previous device owner, or have an Apple accepted proof or purchase:

● Read this article for disabling Find My if Activation Lock has not yet engaged --> Turn off Find My on your devices and items - Apple Support , or this one to learn how to remove Activation Lock either on the device itself or on the web --> How to remove Activation Lock - Apple Support

● For your friend --> Help with a missing Apple ID or password:

• For help with a forgotten Apple ID (this is likely an active email address or one used in the past), click here --> If you forgot your Apple Account primary email address or phone number - Apple Support

• For help with a forgotten Apple Account password, click here --> If you forgot your Apple Account password - Apple Support

• If the previous owner is deceased, read —> How to request access to a deceased family member’s Apple Account - Apple Support

● Reset device if you can prove to Apple's satisfaction you are the owner:

Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. This is done online* at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not provide many details in the article as to what is acceptable proof. Prior to this official service Apple typically required the original receipt** issued by Apple or an Apple Authorized Reseller. Note that while this will let you get use of the device again, it will not help you with lost access to an account. In addition, Apple will not reset if Lost Mode is set on a device.

* There is a special link for this service. To save time you should use it instead of https://getsupport.apple.com/

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

Are you telling us that this is a used phone that is Activation Locked?

Activation Lock is an anti-theft measure that you cannot bypass. The owner to whom the phone is locked will need to unlock the phone for you. Apple does not get involved in second-hand sales and will not unlock the phone on the basis of a receipt for a second-hand sale.

If a phone is Activation Locked and in Lost Mode ("Locked to Owner"), it will be a useless "brick". But even if it is not in Lost Mode, you'll never be able to set it up properly for yourself as long as it is registered to a previous owner.

It seems to me that you have only a few options:

• Get the person who you bought the phone from to take the steps necessary to get back into their Apple account, so that they can then release the Activation Lock and prepare the phone for a new owner (How to remove Activation Lock - Apple Support, What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support).
• Get the seller to file an Activation Lock support request. This requires proof of original purchase from Apple or Apple Authorized Reseller, and the phone must not be in Lost Mode. If Apple grants the request, the seller could then prepare the phone for a new owner.
• Return the phone to the seller and get your money back.
• Chalk this up as an expensive lesson on what not to do when buying a phone the next time.

At least it sounds like the seller has not conveniently "disappeared", or stopped communicating with you, as occurs in far too many of these cases. With luck, maybe they will be willing and able to help you gain full access to the phone.

The All Too Common SAD Reality of Buying a Used iPad/iPhone – Apple Community

Given what you are telling us, that phone will remain Activation Locked. Apple will not remove Activation Lock on the basis of a second-hand sales receipt. It also sounds like the seller is unable or unwilling to assist you in removing the Activation Lock, and unwilling to refund your money.

Sounds like this is going to be a lesson in how not to buy a phone next time.

P.S. - This is a user to user forum. You are not speaking to Apple here.

P.S. – This is a user-to-user forum. Apple largely is not here except to moderate it, and thus, you are not speaking to Apple, but to other users such as yourself.