Please provide a lot more details.
I'm speaking French so my English is poor... but I try to explain my problem...
When I am on Lightroom on a photo, I make all my adjustment but after I want to go on Photoshop with this photo. So I click on Photo in the menu and in Modify in or with (in French it's Modifier dans). I see Modify in Photoshop (ctrl E) but I dont have the access to Photoshop. Why?
Do you have Photoshop on your computer? If so, what version of Photoshop? And also please state the version NUMBER of Lightroom (go to Help->System Info and report the version number shown there).
Yes Photoshop CS5 and Lightroom 6.7 (1090788)
Is the file you are trying to edit actually available?
If it is a smart Preview you won't be able to edit it.
If its missing you won't be able to edit it.
In Library, select the image and choose Photo > Show in Finder (Explorer)
this will indicate if the file is available.
CS5 is an old version of Photoshop.
If you are using NEF or CR2 or other raw files, is your camera supported by the version of ACR for that old version of Photoshop?