Auto-spellchecking suddenly not apparent

Version: 7.4.5.1 / LibreOffice Community
Build ID: 40(Build:1)
CPU threads: 2; OS: Linux 5.15; UI render: default; VCL: gtk3
Locale: en-US (en_US.utf8); UI: en-US
7.4.5-1

Automatic spell-check was in use last x weeks. Yesterday user enabled additionally LanguageTool -from that point of time on both ran parallel, in the same time. Subsequently results of both LO built-in auto spell-check and languagetool work was apparent in document pretty well. Then user examined Language Settings to look if any interesting parameters are present over there. Maybe few of them were enabled then back disabled, or vice versa. Document opening and closing due to quite different reasons. Finally the work of LO built-in auto spellcheck and language tool is document no more apparent - absolutely zero wave-underlying in document view.
Although shortly before there were numerous.

User can find no mistake in Language Settings, nor Tools menu (Writer menu bar) and related sub-menus over there.

Check if user has set language to None either from the Tools menu or in Language Settings. You can tell from the bottom status bar.

Tools menu, menu bar > Automatic spellchecking was of right now. I enabled it and got what user wants.
Strange as that setting was toggled before, those times without effect.

Language was set to same as document language.