Can't paste contents of clipboard into forms in Base

I am using form view to enter data into my tables. I am unable to copy and paste text into a text box in my form that is linked to a data field in my table. I can type text in the box, which is then saved to the corresponding field in my table, but whether I copy just one word or several words, although the selection is copied to the clipboard and the Paste option is “live” in the drop-down menu in the form window, nothing appears when I click Paste. I am sure there is a simple explanation, but can’t figure it out. Have experimented with the Text Box Control properties, to no avail.

My OS is OSX 10.9.5

The text box properties include -
Max text length = 0
Enabled = yes
Visible = yes
Read Only = no
Text type = multi-line
text line ends with : LF (unix)
Hide selection = no

Any suggestions as to where I am going wrong?