The time you save file in Photoshop , I believe you are doing File >Save
Also please try a thing please Close Lightroom and reopen LR, once you save the image in Photoshop.
If that does not help, please remove the Previews Folder of Lightroom and then launch Lightroom.
That does it but. I really don't feel like closing lightroom everytime I edit a photo in photoshop.
So it seems an issue with the previews not getting generated, so I would suggest you to please delete the Previews Folder of Lightroom.
And then Reopen Lightroom, it should take care of the issue.
I am pretty sure this is a known bug in Lightroom CC 2015.1 that I have seen acknowledged here and that is not fixed by clearing ACR cache or by regenerating previews. I know this has happened ever since the LR 2015.1 update. I haven't checked whether this is fixed now in the 2015.2.1 update.
This bug is fixed in Lightroom 2015.2.1. I just tested. I would normally recommend you update but there are many other bugs in it that weren't in LR 2015.1 , so be cautious.
This bug has been reported in the official Adobe feedback forum: Lightroom CC 2015.1.1: Develop module doesn't detect external changes to original file. Adobe has said they've been able to reproduce the problem and are working on it. Please add your vote and opinion to that bug report, because even though Adobe has acknowledged the bug doesn't mean they will implement a fix in the next release. Your vote will make it a little more likely that they will prioritize the fix.
This bug is fixed in Lightroom 2015.2.1. I just tested.
I updated the bug report in the feedback forum to include your results, thanks.
Thanks, I remembered a feedback thread but could not find it when I searched the feedback forum otherwise I would have posted there too with my result.
It's NOT fixed in LR CC 2015.2.1!
I just double checked and it's still there. Please be aware that the problem doesn't occur while you are in the first "edit in PS" loop!
So if you right click your raw file and choose "edit in PS", do some changes in PS and save, everything works as expected. LR detects and shows the changes from PS.
But when you then close and re-open LR and choose "edit in PS" on your TIFF file from step one and then "edit original file" - then your changes in PS are not shown in the develop module anymore. Only the library module updates.
Oh so it seems the bug is only partially fixed! It did work right for me within a single session which didn't work correctly before.