I had this problem and was eventually able to figure it out no thanks to Paypal! I updated my primary number in my profile but when I tried to login to paypal it would always want to send the security code to my old phone number. If you have 2-step authentication on your account and you update your phone number to a new one in your profile settings, you will also need to update your security key. Do the following: - Go to My Profile and Settings-->My settings-->Security Key, deactivate your old mobile number and activate your new number. This will update the number that paypal tries to send the security code to for 2-step authentication.
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