This error generally happens due to renamed wp-admin. In order to solve this error you have to go to the respective path which is shown in the error and then you will find that wp-admin is written which should be your custom admin. This wrong path is the actual reason behind the error.
Step::1 Login to your cPanel admin dashboard
Step::2 Click on the File Manager icon under FILES section
Step::3 Next go to public_html and find wp-content folder in your WordPress installation directory
Step::4 Next go to Plugins directory and create a php file
Step::5 You can give any name to this file like “test.php”
Step::6 Once you have created test.php file, right click and choose the Edit option
Step::7 Add the code given below
<?php
$anything = shell_exec('grep -Ril "wp-admin"');
echo "<pre>$anything</pre>";
?>
Step::8 This code will find the “wp-admin” wherever written in the website’s code
Step::9 Save the file and close the editor
Step::10 Open the test.php from new window in your browser and get the output.
This will show you the list of path where wp-admin i.e old path(Default path) is written. You have to replace this old path(custom path) with the new path wherever required to fix the issue.
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