Before officially inviting customers to join your referral program, test the software yourself in these four areas: registration and member sharing, adding new referrals, rewarding members or referrals, and email automation.
Turn off fraud detection first so you can register yourself as a member. After you do, check if you automatically receive an email after signup, how the dashboard looks like, how it allows you to share a referral URL, and if this link brings you to the correct form or landing page.
When your program is already ongoing, you can run two versions of an incentive (fixed value versus percentage), image, call-to-action, and more. Some of the referral tools mentioned earlier have an A/B testing feature, but if your chosen solution doesn't have this, you'll have to determine which segment of your customers you want to test. Then run the test for your control and test groups at the same time for at least two to three weeks.