The version result is required to determine your used Pywikibot version because it is not the current one. Please run

pwb version

In addition we have to know which script are you unsing and the options you have given.

Btw. if you are using upload.py there is a -ignorewarn option which can be set. Refer pwb upload -help for further Information about available Options.

Sorry, forgot about those

Pywikibot: [https] r-pywikibot-core.git (bb333d2, g14032, 2021/01/12, 13:32:59, stable)
Release version: 5.5.0
requests version: 2.22.0
  cacerts: /etc/ssl/certs/ca-certificates.crt
    certificate test: ok
Python: 3.8.5 (default, Jul 28 2020, 12:59:40)
[GCC 9.3.0]
PYWIKIBOT_DIR: Not set
PYWIKIBOT_DIR_PWB:
PYWIKIBOT_NO_USER_CONFIG: Not set
Config base dir: /home/user/pywikibot/core
Usernames for family "ageofempires":
        en: Red Khan Bot

I used -ignorewarn option. The command I'm running is
python3 pwb.py upload -v -ignorewarn '/path/to/file/Britons King Move 3 AoE2.ogg' -descfile:/path/to/file/description.txt

I also tried -ignorewarn:exists, -ignorewarn:fileexists and -ignorewarn:fileexists-forbidden with the same result.

Isn't there a traceback after that ERROR: Upload error:? That might be important.
Anyway 'ignorewarnings' was set to True. Probably you cannot override a given file and there is a restriction made by the site: 'fileexists-forbidden' is an error not just a warning.

Are you sure you have a 'reupload'/'reupload-shared' permission?

Here are all the log entries for this command

As for the restrictions made by the site. That's what I initially thought and here is their answer after I sent them the output in my initial post

From what I am reading from here: https://www.mediawiki.org/wiki/API:Upload#Upload_warnings ignore_warnings must be set to reupload. I do see, however, that pybot is giving an error in reference to ignore_warnings. As far as I am aware, nothing has changed in reference to our API that would differ it from core MediaWiki 1.33. If you have the latest version of pybot and are ignoring warnings, I would suggest filing a bug with pybot here: https://phabricator.wikimedia.org/maniphest/task/create/?projects=PHID-PROJ-orw42whe2lepxc7gghdq (Or hop on their IRC server for consult/triage/bug reporting: https://webchat.freenode.net/?channels=pywikibot)

Let's have a look to user rights:

>>> import pywikibot
>>> site = pywikibot.Site('ageofempires:en')
>>> sorted(site.userinfo['rights'])

What is the result of it?

['abusefilter-log', 'abusefilter-view', 'applychangetags', 'autoconfirmed', 'autopatrol', 'changetags', 'createpage', 'createtalk', 'edit', 'editsemiprotected', 'edittemplates', 'minoredit', 'move', 'move-categorypages', 'move-rootuserpages', 'move-subpages', 'nominornewtalk', 'purge', 'read', 'skipcaptcha', 'upload', 'writeapi']

Also I can upload files with new names (i.e. not re-uploading) using pywikibot.

Thanks! I'll return to Fandom support then.

Still, unfortunately, no luck.
https://ageofempires.fandom.com/wiki/Special:ListGroupRights specifically shows that bots do have the 'reupload' right but I'm still getting no reupload in the rights list

['abusefilter-log', 'abusefilter-view', 'applychangetags', 'autoconfirmed', 'autopatrol', 'changetags', 'createpage', 'createtalk', 'edit', 'editsemiprotected', 'edittemplates', 'minoredit', 'move', 'move-categorypages', 'move-rootuserpages', 'move-subpages', 'nominornewtalk', 'purge', 'read', 'skipcaptcha', 'upload', 'writeapi']

>>> sorted(site.userinfo['groups']) returns this
['*', 'autoconfirmed', 'bot', 'user']

So we are unsure where it is breaking down.

Are you using a BotPassword? If so, make sure you have a grant with the right.

@JJMC89, thanks for help. It looks like the uploadeditmovefile is needed?

In T271871#6745318, @RedKhan16 wrote:

Still, unfortunately, no luck.
https://ageofempires.fandom.com/wiki/Special:ListGroupRights specifically shows that bots do have the 'reupload' right but I'm still getting no reupload in the rights list

I assume you are either not logged in or you are not logged in with your bot account. To verify the following snippet might be usefull:

>>> import pywikibot
>>> site = pywikibot.Site('ageofempires:en')
>>> site.username()
YourUsername
>>> site.logged_in()
True
>>> site.isBot(site.username())
True

What's your result then?

>>> import pywikibot
>>> site = pywikibot.Site('ageofempires:en')
>>> site.username()
'Red Khan Bot'
>>> site.logged_in()
False
>>> site.isBot(site.username())
True

Isn't site = pywikibot.Site('ageofempires:en') supposed to log me in?

In T271871#6745708, @RedKhan16 wrote:

@JJMC89, thanks for help. It looks like the uploadeditmovefile is needed?

Yes

In T271871#6748113, @Xqt wrote:

I assume you are either not logged in or you are not logged in with your bot account.

Since they show as in the bot group, that's not the issue.

Did some experimenting. This sequence works

>>> import pywikibot
>>> site = pywikibot.Site('ageofempires:en')
>>> sorted(site.userinfo['rights'])
['abusefilter-log', 'abusefilter-view', 'applychangetags', 'autoconfirmed', 'autopatrol', 'changetags', 'createpage', 'createtalk', 'edit', 'editsemiprotected', 'edittemplates', 'minoredit', 'move', 'move-categorypages', 'move-rootuserpages', 'move-subpages', 'nominornewtalk', 'purge', 'read', 'skipcaptcha', 'upload', 'writeapi']
>>> site.username()
'Red Khan Bot'
>>> site.logged_in()
True
>>> site.isBot(site.username())
True

In T271871#6745425, @JJMC89 wrote:

Are you using a BotPassword?

Sorry, forgot to answer. Yes indeed, I'm using a BotPassword.
https://ageofempires.fandom.com/wiki/Special:BotPasswords/Red_Khan_Bot

OK, feeling stupid but figure it out now. I had to grant Upload, replace, and move files right on the Special:BotPasswords/Red_Khan_Bot page.
Thanks for help everybody, sorry to bother you.