edits from Photoshop not saving to Lightroom

There are many ways to send an image to PS and it is not exactly clear which one you are using.  The most reliable is the simplest:   for a RAW file in LR, R click and choose Edit in >.  Photoshop ….  (This is the convention, but is user selectable via Preferences).  Edit in PS and use File > Save.  Not Save As, not Save a Copy; only use Save and it should save to LR.  In LR, a new copy should be visible in your Catalogue with the suffix “Edit”.   I think both apps have to running.   Several parts of this process are affected by your Preference Files in PS and LR.  In my case i set PS to send back a TIFF file. 

Since this is a sudden change with no known alteration on your part, i suspect the prefs file is corrupted.   Uninstalling the application will not remove preferences.   Unless you take special steps, i believe PS will pick up the prior prefs file.  

Just to establish the baseline in this workflow:

• Lightroom doesn't support layers and can't read adjustment layers from Photoshop. It can only read flat images.
• When you turn on "maximize compatibility" in Photoshop, it inserts a flat composite in the file, and this Lightroom can read. This flat composite is updated every time you save the file from Photoshop. 
• Lightroom adjustments are parametric (text instructions), stored in the Lightroom catalog, not in the file. It is not baked into the file until you Export or Edit in.
• Those Lightroom adjustments are sent to Photoshop as a flat file, any previous layers are ignored.

The point is, a round-trip workflow requires that you keep a straight head. A file isn't immediately compatible both ways. My advice is usually to go one way from Lightroom to Photoshop, but not the other way, unless you're absolutely certain that you understand the implications.

Another thing is that Photoshop doesn't save "to" Lightroom, it just saves to disk. It is added to the Lightroom catalog by a background script that tracks the file as long as both applications are open.

So. Please describe exactly what you're doing, and what adjustments have been done where and how.