Overview of the Issue
You might encounter issues with The Events Calendar plugin where specific default strings such as ‘Upcoming’, ‘Previous Events’, and ‘Next Events’ do not display in their translated forms on the Event Archive page when using non-block themes like Twenty Twenty-One.
Workaround
This issue is fixed. Updating to the latest version solves it on your site, so you only need this workaround if you can’t update yet.
Update The Events Calendar and WPML to their latest versions. With The Events Calendar 6.18.0 and a classic theme, these strings show translated.