Iddly by Colorlib error problems

[ Moderator note: moved to Fixing WordPress. ]

I downloaded Iddly, have found it very difficult to work with so looked at changing to a different one page theme.
I am unable to edit the or change because of the following error message.
I have used wordpress for 5 years and never had a problem before. HELP please

Fatal error: Class ‘Epsilon_Editor_Custom_Control’ not found in /var/sites/t/taurus-foundation.org.uk/public_html/wp-content/plugins/illdy-companion/illdy-companion.php on line 345