The in-game config is inaccessible - the automatic in-game message is that FTB GUI Library needs to be installed (It is... both mods are updated to their respective latest release versions.):

(Using Forge 36.2.8)
ftb-library-forge-1605.3.3-build.74
jei-1.16.5-7.7.1.126.jar

From previous threads it sounds like FTB GUI Library has changed it's name and that reference needs to be remedied within the JEI code which is looking for it.

I'm having the same issue

I found the solution in another issue #2521

But even if I change the gui to show more then just 9 columns, it keep at 9, the default is 7, but if i put 2 or 20, it keep showing 9

The linked isn't a solution - it's a workaround by adding a separate mod. The current release jei-1.16.5-7.7.1.126 is not working as intended.

Thanks for the report!
It seems like FTB Library hasn't been very dependable, I have removed support for it and now recommend installing the Configured mod to configure mods in-game. Sorry, I wish this was built into Forge like in previous versions.