LR catalogues won't open off external hard drive like they used to, getting "Lightroom Catalogs can not be opened on network volumes, removable storage, or read only volumes"

You’ve posted to a very old thread. It is highly unlikely that the issue described in this thread, though not impossible, is the same issue which you are currently experiencing. Rather than resurrect an old thread that is seemingly similar, you are better posting to a new thread with fresh, complete information including system information, a complete description of the problem and step-by-step instructions for reproduction. 

In the unlikely event the issue is the same, we will merge you back into the appropriate location. 

Thank you!

Is it plugged into the computer you are using? If it is then it is local.

For whatever reason LR is seeing that drive, Volume, as Read Only and your Username does not have Read and Write permissions. In Windows speak Full Control.

Since this is an external drive it also might be that external is not getting the Drive letter D. If you connected some other external drive first then that external that has your images and catalog on it Windows will assign a drive letter after D. Open up File Explorer and check to see if that external has the drive letter D.