Hey DONJ67,
We understand that you're not able to attach files while using the Yahoo webmail site with Safari. Does this happen when using the Mail app too, or do you only use webmail? You may also consider clearing your browsing history to see if something in the history is causing this to happen: Clear your browsing history in Safari on Mac
Does the same thing happen if you use a different browser? If so, you may consider reaching out to Yahoo Support to look into this: Help for your Yahoo account
If it doesn't happen in a different browser, let us know more details:
- Have you ever been able to add an attachment using the webmail service?
- What happens when you try to attach a file? Does an alert appear or something different?
The more details you can provide the better.
Take care.