[Piklist] Cannot unset string offsets error

I am receiving the following error when I try to activate Piklist on a new installation of WordPress:
Fatal error: Cannot unset string offsets in /var/www/public/wp-content/plugins/piklist/includes/class-piklist.php on line 1212

I looked through the support forum and found a possible solution (https://wordpress.org/support/topic/fatal-error-cannot-unset-string-offsets?replies=14), but did not have the ftp_credentials in the wp_options table. I was not seeing any other help with this type of error.

I am new to WordPress (we are moving over from Drupal). Any suggestions/help would be greatly appreciated!

Lynn