I bought and installed this game a few days ago and had no troubles playing it until today.
When I start the launcher I get a message telling me the item has been moved or changed (I haven't done this) and wants me to reinstall the game.
All the game files are there, and I only bought the game because I was having a similar problem with my disc version.
This is also the first game I have bought with GOG so I don't know if this is just a common site based problem.

Any help or tips in fixing this issue would be appreciated

Thanks! :)

This also happened to me earlier this week - "pharaoh.exe" was moved or deleted.

It turned out that Avast antmalware had quarantined it, believeing it was infected.

This is likely a false positive. Solution:

(1) Look in your antimalware quarantine folder, if "pharaoh.exe" is there, then
(2) Check the file against a universal tool such as virustotal.com (II do NOT work fror them - according to wikipedia they are owned by Google, so using this site should be OK) and see if it agrees the file is clean
(3) restore pharaoh.exe (un-quarantine it).

In my case I had to do (3) before (2) but the order listed is the safest.