Words Vanished in Horizontal Nav

I am using your pligin and the Navigation Menu that comes with it. Text colour is set correctly. I have checked the HTML and the words are in the code. I have checked the CSS and there is nothing that I can see that is wrong. However, when using the inspector tool you see the words isn’t being displayed there are just cubes of 30px x 30px

I have no idea why this has suddenly happened. I hope you can help.

If you need me to post code let me know what you need.

Thanks in advance