Language problem - not take keys from en_GB.ini file

Hello,
- I have added the pl_PL.ini file in to /administrator/components/com_chronoforums2/chronoforums/locales/
- I have changed the en_GB.ini file in to polish translation in /administrator/components/com_chronoforums2/chronoforums/locales/
- all the directories in this path and the files in /locales has the 775 user rights
- on the ChronoForum2 there is language taken not from pl_PL.ini nor en_GB.ini file!
How it is possible? What can I do else?
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ChronoForums2 v.2.0.11
Joomla v.3.9.18

Then maybe there is a problem with the ini file parsing!
​
what happens when you generate a locale then translate one string, does the translation work ?

On my server in ChronoForums2 menu Languages manager I have:
- write "en_GB" and click "Read existing custom file" - there is opened my translation file (i have put my translation also in en_GB file)
- write "pl_PL" and click "Read existing custom file" - there is opened my translation file
- in both situations when I change anything and click "Update custom file" - there is message "The language file has been saved successfully" and the changes are written in the respective ".custom" files
But on the website there is still language taken not from any of this files. Where is now my ChronoForums2 taking the translation from?
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I have put my website on localhost and everything is working without any problem.
I have try it also on some other server in another hosting - everything is working without any problem.
But on my server the ChronoForums2 is still not taking the language from the file en_GB.ini nor pl_PL.ini in /administrator/components/com_chronoforums2/chronoforums/locales/

Did anyone has some idea where could be the problem?

Or:
Where is the base english text which is showed when there are no files in
/administrator/components/com_chronoforums2/chronoforums/locales/
???

I have looked all the file and there is no problem with the file parsing.

then:
- in menu "Language" I have wroten "pl_PL"
- then I have clicked "Build language file"
- I have changed the LAST_POST string
- clicked "Update language file"
- cleared cache
- refreshed webpage
unfortunately nothis has changed...

This is the best forum for Joomla I have seen but now I am blocked with this problem...
Please help me