That’s because those models were created using a geometric modeling kernel that Shapr3D no longer uses—Open Cascade. Since 2017 (iPadOS app version 3.0), the app’s been running on Parasolid, a kernel that guarantees a reliable, stable, high-quality app experience and CAD compatibility.
If you’d still like to work on legacy models in the latest version of Shapr3D, please submit a support ticket here and attach the models. The team will help you convert them into a Parasolid-compatible format.