Your web server is not properly set up to resolve "/ocm-provider/"

ℹ️ Support
102

This was solution for me (put in nginx site config): location ~ ^/(?:ocm-provider).* { rewrite ^ /index.php$request_uri; }

103

FWIW, my issue with ocm-provider was solved by letting Apache know to read the .htaccess file, there was nothing wrong with the contents of the file itself, the OCM line worked fine.

a2ensite nextcloud.conf

this conf file had the notice to allow htaccess files in the nextcloud dir on my server:

<Directory /var/www/nextcloud/>
  Require all granted
  AllowOverride All
  Options FollowSymLinks MultiViews

  <IfModule mod_dav.c>
    Dav off
  </IfModule>
</Directory>

I won’t pretend to say this will fix it for everyone/anyone, this server has been upgraded so many times I imagine my install is pretty bespoke at this point. But I thought I would add in case anyone was wondering why the heck no matter what they edited in the htaccess file, nothing was happening.