There might be some up-gradation issue for the plugin, can you please try to delete the “app_pos” option from the “wp_options” table in the Database.
Alternatively, You follow the steps below to fix the issue:
-Take the backup of the client Id and secret for all the custom applications you have set up.
-Deactivate and delete the currently installed plugin.
-Then activate the plugin which you have downloaded from Login.xecurify.com.