How do I install a language pack?

I did as you wrote
1. I downloaded the FlexiContent language pack again today:
>>> www.flexicontent.org/downloads/download-...on-flexicontent.html
>>> pl-PL.com_flexicontent.zip

2. I installed using:
>>> Joomla > Extension > Manage > Install > Upload Package File> pl-PL.com_flexicontent.zip

3. I logged out of Joomla.

4. I logged in to Joomla by choosing the default language (my default language is Polish) - no translation.

5. I logged in to Joomla by selecting (test) Polish - no translation.

Do you want to access Joomla with administrator privileges? Where should I submit?

Hello

yes you can send me a PM with super admin login

The language files are broken. I have the same problem here with the German translation.
If you look inside the ZIP files there is only the XML inside but no INI Files with the translation. I tried another language and it's the same problem!

Hello

yes the problem with auto-creating the language pack is happening again or was not fixed
unfortunately the extension used to auto-generate them was last updated in 2013

will find an alternative or will try to patch the language extension

Thank you very much for help. I am waiting for information.

Regards

Hello

language packages are now properly created

please retry to download