The Fields and Views button on the paragraph block mini toolbar does not work in WordPress 5.4.
I tried rolling back to WordPress 5.3. Then this problem does not occur.
As for the theme, I tried both Astra and Twenty-Twenty, but the results were the same.
Note:It has been confirmed in a newly installed environment of WordPress.
This should be fixed in the latest release of Access, and in the latest beta release of Views. The latest Views Beta release will be updated to a stable version around next week.
Toolset Views Beta could be installed thru the Toolset Installer, however, we recommend only using beta versions on staging sites, or at least after making a valid backup, if on live sites.
I'll update again here once the Views stable release is also available