New affiliate cannot find my program in their Select Merchant menu

That indicates the affiliate has not actually joined your program yet. They just need to log into the E-junkie account they already registered, stay logged in, and then click your sign-up link again. This troubleshooting page for affiliates explains in more detail.

If that still doesn't work, make sure the sign-up link you are using is exactly the same as the sign-up link code we provide in your Seller Admin > Manage Affiliate Program > Affiliate Program Settings screen. If you wish, you can obtain the href= URL from that link code (e.g. https://www.e-junkie.com/affiliates/?cl=XXXXXX&ev=YYYYYYYYYY) and provide that to your affiliates via email or anywhere you can't paste the full HTML sign-up link code, but take care to provide that actual URL as-is, rather than the URL of the landing page it redirects to.

Also, if you have previously Deleted an affiliate from your program, they would be banned from rejoining your program. You can manually reinstate Deleted affiliates by going to Seller Admin > Manage Affiliate Program > View/Edit Affiliates, then enter their Affiliate ID# in the space indicated and click Undelete Affiliate.