[NSFW] Subscription Confirmation Email in Wrong Language

I have the Jetpack Newsletter subscription widget on the sidebar of the Blog page. The site itself is multilingual and uses WPML to provide translations in English and Spanish.

Problem:
For some reason, when users subscribe to the blog, it gives them the Confirmation and Welcome email in Spanish. But the default language for this site is “English”.

Troubleshooting:
I though it might have been a caching issue from previously viewing the page in Spanish, so I tried in a totally new browser in private mode, and only accessed the site in English, and it still gave me the Spanish version. This has been tested with 3 different email accounts, all giving us the same result. Also worth mentioning: I have not set a custom Welcome Message in the Jetpack Newsletter settings, so it should be displaying the default message.

Also, I checked NSFW because the website is for aesthetic surgeries and contains some images that may not be suitable for work.

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