I am having trouble solidifying an imported surface into a solid body. I have attached a picture as reference. I noticed there was an open surface at one of the faces (it is the sketched out in the second picture) and tried enclosing the volume via an swept surface feature in attempt to Knit the surfaces together and solidify the enclosed volume. However, this did not work. I was inherited this part and cannot obtain the original IGS file. Is there any hope for me to solidify the body or would it be best to remodel this part?

Note: The file is quite messy as there are many other features in the part, however, I have suppressed all the superfluous features and left only the vital imported features that are in regard to the shell volume I wish to enclose.