I cant change video file name and add extension in chromOS

[Zuzia]

Hi i have 1 problem if i wont rename file without extension option rename file is grey and i must rename that file in other system. I talk about local file on usb device not google drive. Example: My file is some video.mp4 but file name now is "video" when i try change name and add extension *.mp4 ChromOS option (Rename ctrl+enter) in menu is grey and my file not work in player, only send me to chrome store, for other addons. Then i change name in windows and all work. Quesion how i can add extension on chromebook. Rly wierd. 1 time i have problem like this. I wont do this on my USB drive connect to chromebook but i must back to windows and this is little annoing. Other folder and file on this same usb i can rename normal but his extension is added. 1 word: if file not have extension in ChromOS i cant change file name. And without extension player not work even if i drag and drop file on player. Where i can write about this bug and inform google? Is any official chromeOS forum for this? I wont report this. Thank You Cheers from Poland.