@veejayka as in the individual items in your menu bar app are all blank? My first guess is that there are keys in your configuration profile without a valid value - i.e. a configuration created in Jamf Pro without the blank "unused" keys removed. 

Yes, when the menu is clicked all the options are there, but simply not visible in text. Just appears blank, but you can hover over it and able to click. I'm not entirely sure what you mean about 'My first guess is that there are keys in your configuration profile without a valid value - i.e. a configuration created in Jamf Pro without the blank "unused" keys removed.' - please could you let me know how I can check/amend this?

Your help is truly appreciated.

Try remove the following keys "Custom Menu Item Preferences" in the configuration profile for com.jamf.connect. 
if youre using the jamf applications inbuilt, you should be able to click on  "Add/Remove Properties" and untick the whole section. 

What mike is saying is...the set of keys allow you to change the text in the jamf connect menu, you most likely have them enabled but dont have any text assigned..so its coming up as blank. 

Hope this helps.

Add com.jamf.connect.verify and they'll appear