[Plugin: All in One SEO Pack] Not Found Error When try to save Home title, description or keywords

Hi all!
I have just installed All is one SEO pack on my blog (anas.pk) and when I went to it’s options page and changed a few options as per my requirements such as enabled the plugin, entered home title, description and keywords and clicked on “Update Options” then I got a “404 Not Found” error. Then I hit the back button in my browser and deleted every thing from the Home Title, description and keywords fields leaving the “Enabled” check box, checked and hit the “update options” again and this time there was no problem. But, still if I try to save any one of those three options then I get a Not Found Error. Please note that The URL in the address bar of the browser remains same all the time i.e.:
https://anas.pk/wp-admin/options-general.php?page=all-in-one-seo-pack/aioseop.class.php
So, if for example after getting a Not Found error I manually enter this address in my browser’s address bar then “All in One SEO” options page is still available there. The only difference is that the problematic detail that I previously tried to enter such as Home title, description and/or keywords is not there i.e. not saved.

Please give me some guidence!
I shall be very thankful to you!
Anas.

https://www.ads-software.com/extend/plugins/all-in-one-seo-pack/