Forbidden error when transfering file

I configured my nextcloud server, when I sync files with Android application, I have no problem. When I want to use the Ubuntu desktop application, I have this error :
Error transferring XXXX://XX.XX.XX.XX:XX/nextcloud/remote.php/dav/files/MyProfile/MyFolder/MyFile - server replied: Forbidden (Sabre\DAV\Exception\Forbidden)
I searched a solution before to post, the problem seems knowed but I found a lot of different solution. I don’t want to copy and paste a line of code in a configuration file which could be create a security breach without understand what I do. What is the reason of the error and what is the best solution to fix it, which file should I modify ?