FTP upload and WordPress install errors

Hello Till & Support Team,
I spent all day trying to diagnose and fix the problems described below. Hoping your can help me please.
I am not able to upload files with FTP or with “SSH FTP” using a Shell-User.
My Filezilla FTP client log shows I can login in but not able to upload files:

17:08:13 Status: Connecting to 31.99.88.xx:21... (fake ip)
17:08:13 Status: Connection established, waiting for welcome message...
17:08:14 Status: Initializing TLS...
17:08:14 Status: TLS connection established.
17:08:15 Status: Logged in
17:08:15 Status: Starting upload of H:\_Duplicator_\xx\25jan30bInstaller\installer.php
17:08:15 Command: CWD /web
17:08:15 Response: 250 OK. Current directory is /web
17:08:15 Command: TYPE A
17:08:15 Response: 200 TYPE is now ASCII
17:08:15 Command: PASV
17:08:15 Response: 227 Entering Passive Mode (31,11,11,xx,156,209) (fake ip)
17:08:15 Command: STOR installer.php
17:08:15 Response: 553 Can't open that file: Permission denied​

I believe the problem is as you describe in another post:

Till: "Then the mistake is likely that you put things into the website as root, now all files and folders have wrong owners and can not be changed by a different user than root. To fix that, you must chown all files and folders inside the web directory to the correct user and group, which is the web[ID] user and client[ID] group of the website."​

Therefore, I found a post that suggests running:

ls -lhd /var/www/clients/client1/web3/web
and:
chown -R web3:client1​

But that did not work.
My website and FTP access work well for WEB1 at: /var/www/clients/client1/web1/web
But DOES NOT work for WEB3 at: /var/www/clients/client1/web3/web

Below is what I tried in my ssh terminal:

root@u22x:/home/u22ad#
root@u22x:/home/u22ad# sudo ls -lhd /var/www/clients/client1/web1/web
drwxr-xr-x 8 web1 client1 4.0K Dec 20 14:47 /var/www/clients/client1/web1/web
((Looks ok to me for /web1 above))

root@u22x:/home/u22ad# sudo ls -lhd /var/www/clients/client1/web3/web
drwxr-xr-x 2 nobody nogroup 4.0K Jan 31 16:15 /var/www/clients/client1/web3/web
((Not sure if the above for /web3 is OK?))

root@u22x:/home/u22ad# sudo chown -R web3:client1 /var/www/clients/client1/web3/web/*
chown: cannot access '/var/www/clients/client1/web3/web/*': No such file or directory
root@u22x:/home/u22ad#​

Currently, the /web3/web/ directory is empty as I deleted all files and folders (for a failed WordPress install) using the root user via ssh terminal.

I would be grateful to get your help to resolve this file upload issue so I can complete a fresh WordPress installation.
I am new at Linux Ubuntu (I have a Windows background). Please provide your suggested fix using detailed commands / guidance.

Many thanks.

 

Hello Till,
I don't know how I broke it...
I did as you instructed. I am now able to upload files using Filezilla.
Many thanks to you!

Next, I will upload the latest WordPress files via FTP and attempt to install WordPress. I expect it should work now.