Could you please provide more detail of this problem? How it may be reproduced?
Sorry Igor I've done a clean os installation, so I can't reproduce it in more details. Between I have some post where there are image with long file name and accent letters in it, example
http://www.rally.it/wp-content/uploads/2016/09/004-Rally-Città-di-Roma-Capitale-2016-day3-transcend-rally_it-696x464.jpg
In plesk 12.5 ( where domain is now ) Apache convert the name in 004-Rally-Citta%CC%80-di-Roma-Capitale-2016-day3-transcend-rally_it-696x464.jpg but the real name is 004-Rally-Città-di-Roma-Capitale-2016-day3-transcend-rally_it-696x464.jpg, as you can see it is a long file name with à in it. I have tried to change charset in Onyx and have the same modules of 12.5 but doesn't work, I was still get page not found. Maybe is not related to Onyx and my knowledge of Apache are not so extensive.
I wonder which was your method of Onyx removal?
You can't install 12.5 version back because there have remained a lot of Onyx packages. You can install Plesk 12.5 only on clean OS installation.
I used a script found in knowledge base. The script is for 12.5, but I was hoping that it works with Onyx too.
You can install Plesk 12.5 only on clean OS installation.
I realized that