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Sorry to hear you’re facing problems 
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In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 12.0.2): 15.0.5.3
Operating system and version (eg, Ubuntu 17.04): Kubuntu 18.04
Apache or nginx version (eg, Apache 2.4.25): Snap (I’m not sure which server version it is)
PHP version (eg, 7.1): 7.2.14
The issue you are facing:
Every time I try to connect to the server through WebDav, the server responds with the following output on the Android browser:
OCA\DAV\Connector\Sabre\Exception\PasswordLoginForbiddenpassword login forbidden
This XML file does not appear to have any style information associated with it. The document tree is shown below.
<d:error xmlns:d="DAV:"xmlns:s="http://sabredav.org/ns"xmlns:o="http://owncloud.org/ns">
<s:exception>
OCA\DAV\Connector\Sabre\Exception\PasswordLoginForbidden
</s:exception>
<s:exception>...</s:exception>
<s:message/>
<o:hint xmlns:o="o:">password login forbidden</o:hint>
</d:error>
<d:error xmlns:d="DAV:"xmlns:s="http://sabredav.org/ns"xmlns:o="http://owncloud.org/ns">...
</d:error>
On a Windows browser, it shows this instead:
Nextcloud
Unauthorized
Technical details
Remote Address: -Computer's External IP Address-
Request ID: BT48hYu4BfiuEeQEHKyt
Nextcloud – a safe home for all your data
Is this the first time you’ve seen this error? (Y/N): Yes.
Steps to replicate it:
-
I try to connect to the server through the url on an Android device:
-
I put in the correct username and password when the server requests for the information
-
The resulting output is shown on the website.
3a. On windows computers, instead of showing the XML file error, it shows that I am unauthorized to access the website. Countless reloads will result in the same message, but different “Request ID.”
The output of your Nextcloud log in Admin > Logging:
PASTE HERE
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
PASTE HERE
The output of your Apache/nginx/system log in /var/log/____:
PASTE HERE
Edit: Found that the server was installed using Snap, not Docker.