Tspline topology error and not converting to smooth display

[raymond_raymond_248193]

My tspline body has refused to change to a smooth display after still repairing the body and making necessary changes to the form body. and Fusion 360 says there is a problem with the form body and keeps suggesting I repair the body (on clicking the finish sketch icon), and I have done that repeatedly and found no problem with the body. 

Please, how do I solve this?

Attached below is a link to the design. Please,  somebody should help. its urgent

https://a360.co/3HiB6Xs

[jeff_strater]

The link does not allow download.  If you have a commercial license, be sure to mark "allow download" on the link sharing.  Otherwise, export as a Fusion Archive and attach the F3D file here.