thank you Bernard, I will follow your guidance there. I remember there was an error with the wp-cache plugin, which was deactivated, but it wasnt until later when I deactivated a different elementor blog plugin and then elementor, that I saw they were dissappearing, and that I could no longer reinstall. TO begin with, I lost the option to install. Some support in my hosting site did something to bring back the install option, but then the plugins could not be activated, and the hosting support rightfully said this wasnt their support problem. Yes, each time I install a plugin, i can see in the wp-content/plugins/.
I followed your instructions, and something changed. I deleted unused themes, and followed some site health advice, and I can now install plugins. I still do not know what the issue was. But thank you for you kind advice.