You can disable the plugin from MYSQL database.
Login to MYSQL via PHPmyAdmin
Expand your database and click on wp_options
Find WPS Hide Login in active plugins and click edit
Type a:0:{} and click Go
Login via wp-admin
To use the plugin are you using Apache or IIS?
Apache
In Apache this issue is usually caused by a conflict between WPS Hide Login and another installed plugin.
IIS
In IIS URL rewrites are generally required with WordPress to structure permalinks in an appropriate manner.
If you are using IIS 7 or above, adding the rewrite rule below in you web.config can resolve the issue.
<?xml version=”1.0″ encoding=”UTF-8″?>
<configuration>
<system.webServer>
<rewrite>
<rules>
<rule name=”URLrewrite” stopProcessing=”true”>
<match url=”.*” />
<conditions logicalGrouping=”MatchAll”>
<add input=”{REQUEST_FILENAME}” matchType=”IsFile” negate=”true” />
<add input=”{REQUEST_FILENAME}” matchType=”IsDirectory” negate=”true” />
</conditions>
<action type=”Rewrite” url=”index.php” />
</rule>
</rules>
</rewrite>
</system.webServer>
</configuration>