I don’t know exactly what’s wrong but it looks like a problem with permalinks. Despite what WordPress tells you when you want to delete Polylang, some settings are still leftover which are used when the plugin is re-activated.
Ensure you backup your site content before re-attempting to use Polylang, just in case.
To get a fresh installation of Polylang so you can double check settings, do the following,
STEP 1
Disable the plugin using the dashboard or from the table wp_options in the database itself. To get straight to the respective row, use,
SELECT * FROM wp_options WHERE option_name="active_plugins"
The option_value will show something like the following,
a:1:{i:0;s:21:"polylang/polylang.php";}
Save this content in case you mess up. To deactivate the plugin, delete from i until the ; which includes polylang as there will be other plugins as well depending on your installation. As soon as you do this, the plugin will be deactivated.
STEP 2
Now we need to tell the polylang plugin to delete its settings when we delete it from the Dashboard. Take care to ensure your content is backed up just in case, you are responsible for this. We will need to to do this procedure from the database itself as the settings menu is only available when Polylang is activated which we cannot do in this case as it will disable access to even the Dashboard.
The required row can be accessed as follows,
SELECT * from wp_options where option_name="polylang"
It will give you the following,
a:12:{s:7:"browser";i:1;s:7:"rewrite";i:1;s:12:"hide_default";i:0;s:10:"force_lang";i:1;s:13:"redirect_lang";i:0;s:13:"media_support";i:1;s:9:"uninstall";i:0;s:4:"sync";a:0:{}s:10:"post_types";a:0:{}s:10:"taxonomies";a:0:{}s:7:"domains";a:0:{}s:7:"version";s:5:"2.0.5";}
where the entry of interest is,
s:9:"uninstall";i:0;
change i:0 to i:1 which would then look like,
s:9:"uninstall";i:1;
STEP 3
Delete the plugin from the Dashboard and reinstall. Everything should be fine now and you can start over with customizing Polylang.
I hope this helps.
