Hello,
This is because you have protected your text field on AnkiHub.
Please unprotect it and do this afterwards:
Please try resetting your local changes. To do this:
Go to browse in your Anki → at the top click on ankihub addon tab → press reset all local changes
This will restore everything to what AnkiHub has unless you have specifically protected those fields
See this for a more in-depth tutorial, specifically the second section: Why are my cards blank/empty when reviewing?