I had this problem a while ago. Tried to get a solution through the autodesk ep support but did not help.
I’ve found an solution that Works for me. Dynamo Player grays out after assigning an directory folder.
You can get the Player working again after deleting the following file “dynamoplayerinstance 1”. Its located here: C:\Users\USERID\AppData\Local\dynamoplayer\User data
Use your own user id.
To keep it working, copy your dynamo files in the default “sample” directory (instead of assigning an folder again) and refresh.
Let me know if It Works!