ftp_mkdir (): create directory operation failed

Hello,

I'm quiet new to this whole OC thingy, and im running into alot of things i fail at! I've been busy for about a week non-stop to get the opencart site running on a server in my own network. After a day or so i had te server with ubuntu 16.10 server running along with Ajenti webadmin. Then a day or what later i got the first sight of the opencart webpage. Then came the real trouble!!

I wanted to be able to import my dealers CSV file so i was planning on finding a proper CSV import tool. When i was installing it trough the extension installer i got alot of error, but the error i cannot fix is this one:

ftp_mkdir (): create directory operation failed. in <b> var/www/html/admin/controller/extensions/installer.php </b> on line 337.

So at first i tought my FTP settings were wrong or my chown settings so i changed the following things:
- in the apache settings i changed the username from www-data to <myusername> and same with group
- then i gave chown to var/www/html/ along with chmod 755/777 (tried both)
- then i installed filezilla and logged in with the same password and username i use in opencart admin settings. Everything works like a charm, without error!

I have opencart version 2.3.0.2, running on ubuntu server 16.10. I have VSFTPD for FTP server running.
I'm accessing it from a different pc(windows 10 trough the local network(192.168.11.*). It finds the website and i can add/delete products and categories etc.

I've been searching the web for days now and i cannot find a solution and its driving me NUTS!

So please, pritty please! Can someone provide me with some intel on this or even a solution?? :)

Thanks in advance!