This is a copy of what you will find in Help
The Clipboard toolbar no longer appears when I copy and paste items.
If you close the Clipboard toolbar three times in a row without using
the Paste All button or any of the item buttons, the Clipboard toolbar
will no longer appear automatically. To show the Clipboard toolbar
again, point to Toolbars on the View menu, and then click Clipboard. You
can also show the Clipboard toolbar again by copying an item two times
consecutively.
When you display the Clipboard toolbar manually and then click Paste All
or click an individual item, the count is reset. From that point on,
the Clipboard toolbar appears automatically again.