Go to: /plugins/import_manager/components/migrators/whmcs/whmcs_migrator.php

Find: $pricing = $this->getOptionPricing($this->WhmcsServices->getTerm($option->billingcycle), $value_id, $currency);

Replace with:

$pricing = $this->getOptionPricing($this->WhmcsServices->getTerm($option->billingcycle), $value_id, $currency);
        if (!$pricing) {
            continue;
        }