Part name and Assembly file

Anytime you need to change the part name use the SW Explorer or with 2018 you can change the name while you're in the assembly file, by right clicking the part in the feature tree and selecting re-name..

The part File Name is linked and if you make any changes the Assembly and Drawing will not recognize the part..

Maha one way to do this is to have the assy and the part model open. Then save the part model, save as xxx, and then it will update the assy at the same time. Now with it as shown here, what you can do is open the part by right clicking on the part model in the tree. Then once you find the part manually open it and then you can unsupress the remainder of the parts in the assy and it will reconnect them.

The answer John Stoltzfus gave you will tell you how to prevent it from happening in the future.  See My Drawing or Assembly can't find dependent files. to fix the problem you have now.  You could also use the method Daniel R. Melendez posted, but that will result in an extra Part file that you'll need to delete from a folder (the original file with the original name).

There is this option as well (however, I haven't ever used it, not do I know if it uses the same methodology as SW explorer):

If you HAVE renamed the part and now the assembly can't find the file and you can't figure out how to reconnect the file tot he assembly, then do a couple of things:

First of all, look here to see if you checked "Do not show again" in an error message regarding the lost component.

Then, simple try to unsuppress the part, which will pop up a window in which it will ask you to browse for the new correct file.