Nextcloud client on unbuntu 18.04 lts problem

Hello all,
I have installed nextcloud server. And also nextcloud client on my computer. Its function is good. Except when I launch nextcloud desktop sync client it opens. I see there three dots on de right side above. When I click on it, I get the possibility to open the folder. But that does not work. I see also een green dot on my screen right above. When I click on it,it pops down and I see different possibilities: open nextcloud in browser, open folder ‘nextcloud’, recent changes,…when I click on them, it does not work.
Whats the solution for it?

I see also in settings…>online accounts…> nextcloud.
Do I have to do something wit that?

Thanks for your reactions!