Unable to Open Project Error

[scott.dennisjr]

All of a sudden with no discernible reason whatsoever I am getting this error message when I try to open a Project File in Autocad Plant 3D. My other project files open just fine. 

[h_eger]

Dear @scott.dennisjr ,

Plant 3D close. Check which lock files are still available in your project folder. (* .plk, * .lock)
delete if any and start again.

[scott.dennisjr]

Deleted all .plk & .lock files, closed and re-opened Autocad Plant 3D, still getting same error message when I try to open the project.