Translation not available

Go to the Advanced Settings menu of the plugin and make sure the following option is enabled (we recommend using the new registration form):

Activate New Form and Validation Interface

Next, check that your language’s translation file is up to date. An outdated file may be missing some translation strings. You can follow the steps in the documentation below to update the file and add any missing translations:

https://simple-membership-plugin.com/translate-simple-membership-plugin/#existing-file-translation-update-steps

Here is the main POT file of the plugin, which confirms that the strings are definitely included:
https://github.com/wp-insider/simple-membership/blob/7ec972b810fb9591e627c7e78b7a92b9ebcd8283/simple-membership/languages/simple-membership.pot#L986-L999

Please note, we don’t maintain the translated language files or their associated POT files. These are typically contributed by users. When a user sends us an updated pair of .po and .mo files for a language, we include them in the plugin.

So if your language file is missing some strings, it’s likely because that language’s translation files are outdated. You’ll need to use the main POT file to update your own language file and then perform the translation. The documentation I previously shared outlines how to do this step by step.