When I first installed grav for this blog, the admin plugin was pretty new and it was not that easy to install grav on OVH (at least on a PRO hosting) because of a limitation with their SSH access which does not allow downloading internet data from the command line. Grav relies heavily on bin/grav to process (very efficiently) basic operations and lot of them need to harvest information from the web which is not possible. So back in time for my first install, I had been obliged to install locally my grav instance before copying here over FTP...
Today I have installed a new CMS blog based on grav (yes, I really like this CMS for its simplicity and the dynamism of the project, almost an update each week, if not more frequently, at the moment) on another OVH hosting. And things have changed, it is now so easy that I am not even sure that this post will be useful but who knows!
So first thing is to download Grav (but if you are there it is certainly already done), being careful to download the "Grav core + admin plugin", that will definitely make things easier. Copy them over your server via FTP, then access the URL where you have copied things. You should see the following error claiming that "/bin/grav is not executable", "/bin/composer.phar is not executable" and so on:
To change that, just navigate to the folder where you have copied the file (I use filezilla and right click on the 4 files in the bin directory then choose the last option to change the attributes of the files (not sure of the exact wording, my filezilla is not in English), and choose to give the "execute" right to the owner of the files as outlined in red below (that can also be done via SSH, using the chmod command):
Just refresh the file with the error that you had previously, everything should work fine!