Have a problem with plugin

Hi!
I found a bug in your plugin. Could you please obsolete it and update the plugin with version 5.5.1 of WordPress?

The error is due to the fact that the plugin writes that the letter was sent to the mail, but there is no letter in the mail, neither in the spam folder, nor in the inbox either. There is nowhere. How can I remove this message and use your plugin, so as not to display pinned posts too. Please fix bugs and update the plugin if possible.
Plugin
https://www.ads-software.com/plugins/ultimate-posts-widget/

I attachment a photo with errors
https://drive.google.com/file/d/1IqJ_18lgpxrcX8FAcYpHUZ22cYvhkh8v/view?usp=sharing