Errors in Admin After Latest Upgrade

Since the latest MailPoet 3 update was installed on our site, I now consistently get the following error at the bottom of all MailPoet dashboard pages in the admin –

Purge individual files by URL
You can purge up to 30 files at a time.

Note: Wildcards are not supported with single file purge at this time. You will need to specify the full path to the file.

Separate URL(s) with spaces, or list one per line

The page I need help with: [log in to see the link]