YITH Plugin Error

I have used Highend for many different clients and have had a great experience, which is why I keep purchasing the theme. I recently had purchased a customization done with HB Themes that used the YITH plugin and I am getting the following error messages:

There is a warning message on the top of all WordPress admin pages that is related to the YITH donations plugin:

Warning: Declaration of YITH_WC_Donations_Email::get_content_type() should be compatible with WC_Email::get_content_type($default_content_type = ”) in /home/aocsn297/public_html/wp-content/plugins/yith-donations-for-woocommerce-premium/includes/emails/class.ywcds-donations-email.php on line 7

Everything is updated in the admin except the YITH plugin, but I get this message when I try to update the plugin:

An error occurred while updating YITH Donations for WooCommerce Premium: You have to activate the plugin to benefit from automatic updates.

Please let me know what can be done to remedy the issues related to the YITH plugin, thank you.