Unable to translate activity titles

AFAIK, you can find and translate those strings here: admin/config/regional/translate

Thank you for you comment. I have all strings translated on admin/config/regional/translate still no success

I had the same issue somewhere after updating from 11.6.3 to 11.7.2. Probably with the switch to 11.7.x

The attached patch solved the issue.

Thank you for your answer, your solution allows to change language of the activity titles (to the newly added), but doesn't allow to switch back to the default language

Thanks @tt12, I already learned it the hard way. You will run into some serious trouble with in unicode.php, if no translation is available.
The modified patch works fine for me in my projects.

I have the same issue in 12.4.2.
I checked the code and found the patch, but it didnt work.

I use this solution

/profiles/contrib/social/modules/custom/activity_creator/activity_creator.module

297

- $output = \Drupal::service('activity_creator.activity_factory')->getMessageText($message, \Drupal::languageManager()->getCurrentLanguage()->getId());
+ $output = \Drupal::service('activity_creator.activity_factory')->getMessageText($message);