Not updating because og:locale:locale problem

Hola!
In the site http://cosecharoja.org
I get this error when I actualize an post:

Error: Facebook Open Graph Tags cache NOT updated/purged.
Facebook returned: Object at URL ‘http://cosecharoja.org/denuncian-que-la-policia-torturo-un-militante-gay-en-miramar/’ of type ‘article’ is invalid because the given value ‘es_ar’ for property ‘og:locale:locale’ could not be parsed as type ‘enum’.

any ideas?
thanks in advance,
sebastián

https://wordpress.org/plugins/wp-facebook-open-graph-protocol/