Hello,
My site is no longer accessible (not visible nor via WordPress) and shows the following error:
Not Found
The requested URL was not found on this server.
Apache/2.4.52
OVH cannot help me, could you guide me please?
Thank you very much!
Hello @PatriceL31
Note, this post appears to be a duplicate of this one: Erreur URL non trouvé / Problème Apache
Feel free to share your domain name so we can help you 
Asterix
Yes, I thought it hadn't worked!
It's the site www.traildesmaures.com, thank you very much!
This domain points to a shared hosting on cluster131, and there doesn’t seem to be any issue with it, because the default WordPress files can be accessed:
Have any modifications been made? If so, I will try to restore via FTP:
• Click on your domain under the "Hosting" section,
• Go to the "FTP - SSH" tab,
• Click the "Restore a backup" button,
• Choose the restoration date: J-1, J-2, J-3, S-1 or S-2,
• Wait for the restoration to finish.
Then the site’s database:
• Click on your domain under the "Hosting" section.
• Go to the "Database" tab.
• Click the three dots to the right of your database to restore it.
Astérix
I had restored the FTP backup but not the database… I just did it, so I hope it will work. Thanks for your response.
Hello @PatriceL31
Always:
# Not Found
- The requested URL was not found on this server.*
- ---*
- Apache/2.4.52*
Here’s some wholesome reading!
Here’s a short guide I wrote that could give you some clarity for a complete and clean installation of your site.
Guide - Understanding the Domain > DNS Zone > Hosting > Site Folder
See --> CMS - WordPress - Installation Guide at OVH
Read and check your situation by following the carefully paragraphs: A to J applicable to all CMSs
Feel free to give me feedback: positive or negative.
This is how I fine‑tune my Guide.
If my answer is the solution, feel free to click “Approve the solution”
You're a rockstar, friend @Gaston, I really like your guide 
Thanks @sturpin
Hello @Gaston
Thank you for your response! Indeed the same problem persists despite the restorations. I will read your guide carefully and get back to you! Thank you very much!
Hello,
I have a terrible feeling that your site has been hacked, and that the error message is bogus, because it is generated via PHP and not Apache.
The page http://www.traildesmaures.com/readme.html shows that there is indeed a WordPress at that address.
I would completely reinstall WordPress from a reliable source, following this official guide to the letter:
https://developer.wordpress.org/advanced-administration/upgrade/upgrading/
Basically, you download WordPress.zip from the official wordpress.org site, unzip it locally; it will contain about 6,000 to 7,000 files,
On your hosting, in the wp-content folder, rename the plugins folder to plugins_old. Do the same for themes, also rename it.
Upload everything to your host using SFTP instead of FTP, with the option to overwrite existing files of the same name if needed.
This procedure leaves your wp-content, your wp-config.php, and the database untouched. The content of your site is preserved.
You then need to reinstall the theme you want, as well as the plugins (and install only a strict minimum).
Hello,
Indeed @fritz2cat, I was hacked; it was well hidden in the files... I’ll get everything back in order today. Do you have a good plugin to recommend for WordPress to prevent another possible attempt?
Thanks @Gaston for the booklet; I’ll use your document for any future site creation, I still have to finish going through it.
Thank you very much for your help!
Patrice
Hello @PatriceL31
To avoid all these little hassles, make regular backups on your PC.
This procedure will have eradicated most infections.
Nevertheless, there may still be some files created by the hacker in your hosting that could act as trojans.
Also check in your WordPress admin panel whether the hacker has created one or more users with administrator‑level access rights.
This is to say that you never come away completely unscathed from a hack when you don’t have a backup from before the breach.
To avoid being hacked again, you need good hygiene: keep all components up to date, install only the minimum necessary, and activate only the minimum necessary.
And make backups (outside of the hosting, of course).
Hello @PatriceL31
When your WordPress site is operational again, don’t forget to back it up on your PC.
That will spare you the woes of this repair.
Backups of your site at OVH are not eternal.
Excerpt from my guide: T - Restoring your site on OVH to an earlier date
At OVH, restoring your hosting can only go back up to two weeks at most.
If the hack of your site dates back three weeks, you’re screwed and have to delete everything and completely rebuild your site.
At OVH, restoring your database can only go back up to two months at most.
Remember to make a backup of Hosting and Database on your PC once a month.
See in my guide the section: Ua - Full backup of your site on your PC
See in my guide the section: Ub - Full restoration of your site from your PC