Stop trying to force the cover over the cushion and compare the care label with the washing and drying method used. A cover that no longer fits may pull seams, distort the filling or expose parts that should remain enclosed. Contact the retailer with the product details and explain what happened so they can advise on replacement or the intended refitting method. Do not cut openings or leave a zip partly fastened where the cat can reach the filling. If the bed can be used safely with an approved alternative cover, follow the manufacturer's guidance; otherwise keep it out of use until the fit is resolved. For future purchases, check replacement availability and drying requirements before ordering. A removable cover is helpful only when its care routine and refitting process are practical for the way you will maintain the bed.
Check that the insert is correctly oriented and fully reshaped before concluding the cover has shrunk. A rotated bolster section or bunched filling can also prevent a correctly sized cover from closing.
For product comparisons alongside this advice, see Velvet Nest and Silver Velvet Nest. The details below explain their sizes and uses.
Velvet Nest
Silver Velvet Nest
AeroMat Chill Pad