ERROR & Cannot add dates and times, etc

I love this plug-in BUT for some reason, it is not working with the theme that I purchased…

#1 – when I activate the plug-in, I get this across the screen (on the WP Dashboard AND the website)

lessphp fatal error: parse error: failed at (~".span@{index}") { .span(@index); } /home4/hope2013/public_html/wp-content/themes/HBH-43375/bootstrap/less/mixins.less on line 560lessphp fatal error: parse error: failed at (~".span@{index}") { .span(@index); } /home4/hope2013/public_html/wp-content/themes/HBH-43375/bootstrap/less/mixins.less on line 560

#2 – I can’t add or edit any date/times or event locations.
I can’t complete entries into the fields and
the drop-down arrows don’t work.

#3 – The Setting page (for the plug-in)
When I click on ANY link in the General Settings area, NOTHING happens

This theme uses the Cherry (2.3.1) theme (of which I am NOT a fan but I’ve spent too much time learning all of this to change themes now!)

Any help is appreciated!

(btw – I am using AI1EC Version 2.5.19)