Comcast to Yahoo Migration. Verification problem

Need help with sign in problem involving my Comcast email after it's migrated to Yahoo.

My @comcast.net email account has already been migrated to Yahoo. During the process, Yahoo required me to change PW & i successfully created a new one. The problem is what happened after I enter the PW:

1. I entered my new PW and Yahoo display 'Yahoo needs to verify you'

2. I do not given a clear option showing how to complete the verification. 

3. I do not receive a verification code by text to my phone.

4. If Yahoo attempts to send a verification email to my Comcast mailbox, that's not possible because I can't access the mail box the first place.

5. I have already tried to get help from Xfinity & Yahoo, but being referred back & forth. Xfinity say because the account has been migrated, I need to contact Yahoo. Yahoo required verification step that I cannot complete.

6. This is not simply a PW reset problem. I can enter the new PW that was established during migration. The problem is the verification step that occurs after the PW entered.

7. I am asking for help from an Official Xfinity Employee or someone with technical knowledge of the Comcast to Yahoo migration & authentication  process.

8. Could someone please investigate whether there is a problem with migration, the recovery/verification information associated with the account.

9. If account-specific information is needed, I am happy to provide it thru a private Direct Message after an Official Xfinity Employee request it.

I would appreciate very much if I would hear from the Official Xfinity Employee or anyone who had the sane problem & were able to solve it. Thank you!