Apologies for posting so soon -- after checking a few of my other sites running Wordfence, I see that it is indeed a problem on your end:
"Scan terminated with error: WordFence API error: Wordfence is currently experiencing high load and our servers are giving scan priority to paid customers. Please try your scan again in a few seconds."
However, one site displayed this message when I tried to view how a file had changed after yesterday's last successful scan:
"We could not fetch a core WordPress file from the Wordfence API."
That's a pretty scary message! Perhaps you should consider something less alarming...