SOLVED:When trying to enter in our 'cb activity' frontend box, nothing is saved.

Ok, I've downloaded it, and reinstalled it, but I don't see any change in the saving, if I enter something, it doesn't save.
I do see the comment create and activity comment field appear now, but not an activity create on the frontend for non-superusers.

I just noticed, that pressing enter doesn't submit the comment, it just produces a new line, and there is no submit button?

I just noticed, that pressing enter doesn't submit the comment, it just produces a new line,

Correct.

and there is no submit button?

Button should be bottom right and says "Post". If it's not there then you probably have CSS coming from somewhere hiding it. If you've overridden CB Activity template files then switch CB Activity back to default template and retry. See our demo site below on how it should look and behave by default.

demo.cbdemosites.com/

I see, so the 'post button' only appears when I press inside the window, that sounds like a javascript error.
I've tried disabling all the modules, and I've tried using the beez3 tempalte, none of those changed anything.

I see, so the 'post button' only appears when I press inside the window, that sounds like a javascript error.

Yes, you have to focus the textarea input for the textarea input to expand and all the buttons to be available. If that's not happening for you then you've a fatal JS error present breaking its JS. Press F12 to open your browsers developer console then select the Console tab and refresh the page. Next attempt to use CB Activity and see if any fatal JS errors are present in the console. This is almost always caused by a 3rd party Joomla template or JS compression extensions.

Have reviewed your install. Second time I've seen this issue. Basically some reason CBs jQuery is breaking due to something reassigning cbjQuery variable. Not sure what's doing it, but the solution is to turn off CBs jQuery and utilize Joomlas. I've disabled CBs jQuery within CB > Configuration > Integrations and is working fine now.

Edit: I think I finally see what's causing it. Joomla loaded jQuery and Mootools at same time. Mootools appears to be what's replacing cbjQuery, but I've no idea why. Should be able to reproduce locally now and finally fix this once and for all.