Hi williow80,
welcome to the Apple (user-to-user) Community!
Re: Verification of Phone number not working
Wondering where the verification of phone number is not working:
eg: maybe in an app like Messages, or with iCloud, or with your Apple ID, or with your carrier.
and
whether this is on your iPad, or on a iPhone, and which iOS version you are using
Things you might want to check:
Re: Security: Is there an OS update waiting to install in Settings > General > Software update ?
Who are you verifying the phone number with ... your SIM plan-provider / Apple
Eg: You can check with your carrier that the SMS plan is enabled for the SIM that you have
or
You may need to use an international phone number with country code, not just a local number
You can check your phone number is listed correctly in your Apple ID account:
Eg: How to sign in to your device with your Apple ID: Sign in with your Apple ID - Apple Support
If verifying in the Messages app ... is the phone number listed there or just an email address.
Eg: How to: Add or remove your phone number in Messages or FaceTime - Apple Support
or
Check: Settings > Messages, and tap Send & Receive.
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You can try logging-in to your Apple ID online at https://appleid.apple.com/
See how to: Get a verification code and sign in with two-factor authentication - Apple Support
or
Check carefully through: Two-factor authentication for Apple ID - Apple Support
Hope something here can help :-)