Grafting onto Illinois Everbearing

Grafting Geraldi and Kokuso onto a 2 yr old rooted IE cutting and 5 yr old IE failed. The grafts grew for 3 or 4 weeks and then died. Any chance it was a compatibility problem between them?

Sounds like a likely possibility. What is the Illinois ever bearing grafted on? If it’s a seedling you might be able to graft a seedling on as an interstem to make it work with those varieties. . I do that with pears frequently.