For the past few days I've also been unable to update my FileZilla client. I'm not on any corporate network nor using any 3rd party security software besides the default Windows 10 security settings. Two different WIndows 10 devices with FileZilla 3.56.2 are unable to update. I thought this topic was the same but it may not be. In my case, both devices show an error 500 in the Filezilla client update function log:
Started update check on 2021-11-21 22:45:08
Own build type: official
Requesting
https://update.filezilla-project.org/update.php
Resolving address of update.filezilla-project.org
Connecting to 49.12.121.47:443...
Connection established, initializing TLS...
Verifying certificate...
TLS connection established, sending HTTP request
GET /update.php HTTP/1.1
Connection: close
Host: update.filezilla-project.org
User-Agent: FileZilla/3.56.2
HTTP/1.1 500 Internal Server Error
Date: Mon, 22 Nov 2021 04:45:08 GMT
Server: Apache
Upgrade: h2
Connection: Upgrade, close
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block
X-Frame-Options: deny
Content-Length: 0
Content-Type: text/plain;charset=UTF-8
File transfer failed