Activity Watch has a feature called afk (away from keyboard). Basically what it does is it monitors if there is any keyboard or mouse activity like key presses or clicks, and in their absence it assumes that you have left your pc on and went away,like maybe you are downloading something and don’t want to sit in front of the screen just to see the loading bar.
Now of course, when we are attending a zoom call, we don’t normally keep on fiddling with the keyboard or the mouse, and that leads afk to believe we are not there, and so it does not count that time. Afk is somewhat smart, like if you are watching a movie on vlc for example, it will count the entire time period that app was running, because when people are watching a movie they don’t press any keys and yet they are sitting right there in front of the screen.
I also face the same problem as you, that of zoom calls going unrecorded on aw. I don’t know how to turn off afk, or if that is even possible, but you can go to “filter” on the top right of your “activities” page and then uncheck the “exclude afk time” and it will show you your activities without using the afk feature, i.e. all your zoom call time will be counted.