why am i unable to use my primary email address as my apple id

Hello scacres,

There can be several reasons why an email isn't available. Did you have a chance to look at the reasons showing in the article viewed before posting? Here it is again for you:

Change your Apple ID - Apple Support

If you can't change your Apple ID

* If you try to change your Apple ID to an @icloud.com email address that was created within the last 30 days, you will be asked to try again later.

* If you see a message that the email address you want to use isn't available or is already in use, check that you or a family member aren't already using that email address with a different Apple ID. If a family member is using that email address, remove it from their account then try to use it. 

* In some countries or regions, you can use your phone number as your Apple ID. But if your Apple ID is an email address, you can't change it to a phone number.

And, in addition, if the email is already in use as an Apple ID or associated with an existing Apple ID then it will not be able to be used.

Cheers!