@naibabiji,
did you try saving with that plugin disabled? I tried saving exactly the same settings as you and everything worked fine on my test websites.
Do you see any errors in php error log?
If nothing helps, you can remove the code below in wp-content\plugins\rate-my-post\admin\class-rate-my-post-admin.php from line 205 to line 208:
if ( count( $deafult_options ) !== count( $_POST ) - 2 ) { //action and nonce in post request do not count
echo esc_html__( 'Error saving settings! Try clearing all caches, including your browser cache!', 'rate-my-post' );
die(); //do not proceed
}
This will for sure help but I’m still hoping we can figure out what causes such an issue.
Regards,
Blaz