Are you working on smart previews?
Do you have an exclamation or question mark on your image?
Can you share a screenshot of the library module with us.
I found the solution by chance. After posting here I want to open a picture from my picture-HDD, but it was not in the explorer ...
the harddisk with the photos lost contact, maybe at the SATA-Port ... so lightroom didn´t "see the pictures" and greys out the "edit in"-Option.
After re-pluggin the SATA-Port and a windwows-restart ... everything works in Lightroom/Photoshop. .... puuuh
That is why I asked you check for an exclamation mark or question mark which indicates a file or folder to be missing.
I am glad to know you are able to fix your issue.