Hello @harleynt, sometimes FB onion site has some connectivity issues. Please try their main domain Facebook.com.
FWIW, they use alt-svc to redirect Tor users to their onion site. See Facebook announcement:
When using facebook.com in the Tor Browser, we
serve an HTTP response header called “Alternative
Services” that specifies a different (i.e. onion)
service that the browser can use. We’ve set up
multiple new onion services for this purpose to
help improve reliability and scalability. As a result,
the Tor browser will connect to facebook.com
using an onion service whenever possible. Unlike
our original service facebookcorewwwi.onion,
people no longer have to type in the onion address.
Both the address bar and URLs across the site will
still point to facebook.com.