Wrong size rails, they look too long or too short, they do not fit
You may have them in upside down, even though you see the "This side up" printing on the side rails. You also need to see “This side up” printed on the center of the fabric that connects the two side rails (we call this area the tray). This is common with smart beds that have wrapped rails which are connected by fabric. Please remove and flip your foam rails to make sure that you have unrolled the rails properly. You will want the maximum amount of fabric between them. If there is still fabric is folded under the rail it will not fit properly.