Fatal error, help!

I just updated the plug-in this morning and I’m now getting this error:

Fatal error: Call to undefined function mb_strlen() in /home/cthou0/public_html/wp-content/plugins/list-category-posts/include/lcp-catlistdisplayer.php on line 403

Can you make a recommendation on how I can fix it?

Here’s an example of the query I’ve got inside a text widget:

[catlist name=Zawistowski,Zawistowski_feature title_limit=65 date=yes numberposts=30 pagination=yes]

Or, is there a way I can download the previous version and go back to the one that was working for me? Thanks for your help.

https://ww.wp.xz.cn/plugins/list-category-posts/