Dashboard Language won't change

I have 2 multi-language WP sites. On both, even so I can see and pick different languages under the ‘General Settings” – “Site Language”, I can hit ‘save’ but the language does not change to my updated choice. On one site, it’s not a problem, as it’s ‘stuck’ in English, but on the other site, it’s stuck in Spanish, which I don’t speak. The odd thing on the site stuck in Spanish is that not all the dashboard labels are Spanish, a few are in English.