3D FlipBook - My 3dbook takes a long time to load

Please help me, my 3dbook takes a long time to load or can't open at times. My customers all over the world (mainly in the US and Europe) also report it opening very slowly or not being able to access it. This has had a significant impact on our business. Please help me check and solve. My 3d book page is: https://atc-craft.com/best-selling-catalogue/

Hope to hear from you as soon as possible