Error “Failed to install add on from zip file”

I am doing a new install for Raspberry Pi3. Downloaded Openelec 8.0 with Kodi 17.1.
I added the sources for Fusion, No Limits and SuperRepo through File Manager. Turned on the Unknown. Sources in Settings. I then went back to the main screen and chose Add-ons. Chose the image of the box in the top left corner and clicked on “Install from zip file”.
For Fusion I clicked on the begin-here folder and installed the relevant file. After a short time I got the error message “Failed to install Add-ons from zip file”.

I get this same error message for all add ons I try to install.
Could you please help me with a solution.
Truze