I can't turn on spellchecking sometimes

I’m pressing F7 to start the spellcheck but it appears as if no language was selected.
Other times, it does work.
What should I do to make it work all the time?

Version: 7.1.7.2 (x64) / LibreOffice Community
Build ID: c6a4e3954236145e2acb0b65f68614365aeee33f
CPU threads: 12; OS: Windows 10.0 Build 18363; UI render: Skia/Raster; VCL: win
Locale: hu-HU (ru_RU); UI: en-US
Calc: threaded

EDIT:

I’ve set the language of the text like this:
Tools —> Language —> For All Text —> Hungarian.

These are my language settings:

Please edit your question to tell how you set the language for your text. The current language is shown in the bottom status bar, whether you have set it or not.
Also, what style is in effect in your text (the top toolbar displays it unless you changed the UI for some fancy “ribbon” one).
Have you changed the default language in Tools>Options, Language Settings>Languages?

Please upload a sample document, screenshots and movies don’t tell very much.
A long shot: There was a problem with OpenOffice in Windows: Some users would make new documents by right-clicking in Windows Explorer and selecting New Writer document. The resulting document was based on a faulty template; you couldn’t set a language in it.