If you were to add this to the page only [types termmeta='tax-content' output='raw'][/types] does it return a value ?
You can only retrieve a term meta if :
A) You are using a view that is listing out taxonomy terms.
B) On a taxonomy archive.
If you page is just displaying the post then you won't be able to list the term meta. You will need to create a view that will be added to the page to list out the taxonomies and in that view you can retrieve the term meta.
I'm assuming that this is on a post and the read more should link to the post page.
So in this case you will need to create a taxonomy view and add the query filter for that taxonomy to list the items of the current page. See Screenshot for example .
You will add a taxonomy term filter so it will list the taxonomy for the current page.
[wpv-conditional if="('[types termmeta='tax-content' output='raw'][/types]' ne '')"]
[wpv-post-read-more item="$current_page"] // This is for the read more button
[/wpv-conditional]