Your shipping origin can be edited within your Shipping settings (Admin > Settings > Shipping). From that page, you will see at the top a header that says ‘Shipping Origin’ and some blue text that says 'Change Shipping origin. Example screenshot below:
As far as the error you are seeing at checkout “shipping not available for selected address” is caused by your Shipping settings not including the region that your customer entered as their shipping address. For example, if your customer’s shipping address is in Ontario, Canada but you do not have a shipping zone that includes Canada & Ontario in it, they will not be able to check out. You can add and edit your existing shipping zones to include all the regions you would like to ship to. From there, you can set your shipping rates to charge your customers for each region. More info on setting up shipping zones here.
If there is anything else I can help you with, please let me know.
To access your admin and follow the steps I laid out in my previous post above, you will need to login. To login to your admin, simply type your store name into your browser YOURSTORENAME.myshopify.com**/admin**
Be sure to add the /admin at the end so that it takes you to your login screen. From there, you will enter your password and then be redirected into your backend admin. From there, you can follow the steps I outlined above.
If there is anything else I can help you with, please let me know.
Is there a way you can change my shipping origin? I am still having issues finding the page to change the origin. It is showing my family home as the origin with only the option to remove it, which in turns deactivates shipping all together.