Hi Lilith,
I have also noticed the issue now but as this issue is new and didn't faced yet and I just replicate this with my local machine but did not faced.
I would suggest you to have a clone copy of whole site with different directory or sub domain
to check necessary issue. It may required to disable or uninstall some extensions.
So before inform our developer the issue I prefer to check the issue is causing from our end.
Your co-operation is expected.
Thanks

i made a clone of the site
check your mailbox please.

Hi,
Thanks for your co-operation.
I am taking care the issue and need ftp access of test server (according to private message).
Can you help me?
Thanks

check your mailbox please.

Hi Lilith,
Still experiencing login failed.
May be my Ip blocked.
I have sent my IP, Check PM and unblock the ip.
Thanks

Hi
We are waiting more then a week
Did you find a solution?

Treatment failure persists a long time, it is not right, my site was hit and lost a lot of customers!
I ask your reference as soon as possible!

Hi Lilith,
Sorry for the delay.
I am still experiencing login failed problem with ftp.
Here I have attached a screenshot.
Please care this issue.
Thanks

Your certificate was valid for a week, send me again your IP in private message to give you access.

Hi Lilith,
I have sent my ip at PM.
Please check.
Thanks

Done

Hi Lilith,
Now the ftp access is working fine.
I will be back with update soon.
Thanks

Hi, Lilith.

Error 403 is server related:

A web server may return a 403 Forbidden HTTP status code in response to a request from a client for a web page or resource to indicate that the server can be reached and understood the request, but refuses to take any further action. Status code 403 responses are the result of the web server being configured to deny access, for some reason, to the requested resource by the client.

A typical request that may receive a 403 Forbidden response is a GET for a web page, performed by a web browser to retrieve the page for display to a user in a browser window. The web server may return a 403 Forbidden status for other types of requests as well.

The Apache web server returns 403 Forbidden in response to requests for url paths that correspond to filesystem directories, when directory listings have been disabled in the server. Some administrators configure the mod_proxy extension to Apache to block such requests, and this will also return 403 Forbidden. Microsoft IIS responds in the same way when directory listings are denied in that server. In WebDAV, the 403 Forbidden response will be returned by the server if the client issued a PROPFIND request but did not also issue the required Depth header, or issued a Depth header of infinity.