Stephane Picault 

The error message you mention only appears if you open a project which then tries to open the TMs that are assigned to the project. It means that it cannot find the TM in the given location. This can happen because the TM has been moved or deleted in the meantime. 
The easiest way to correct this is to go to your project settings, remove the TM that cannot be found and add the TM again from the location where it is currently located. 

Good afternoon Walter, 

Thanks very much for the help offered.  However, I am not sure that the solution you suggest applies to my particular case. 

This is what happened: I loaded a translation project into Trados Studion 2017 and opened it.  A TM was supplied separately by the translation agency that is to be used for the translation.  I stored the TM file in a folder next to the folder containing the project.  After opening the project in Trados I then tried to select the TM (via "Project Settings") from its location in the folder, and it was then that I received the error message.  Normally the TM is added to the list of TMs in the top window on the "Project Settings" page after it has been selected.
In the past this has always occurred without any problems. I have had to install Trados anew after my hard drive failed and had to be replaced.  This is my first attempt to use Trados with the new hard drive. 
In the meantime I have moved the TM to another location, but still get the same error message.

Thanks again for your support.

Stephane Picault 

 Stephane Picault 

Stephane Picault said:

After opening the project in Trados I then tried to select the TM (via "Project Settings") from its location in the folder, and it was then that I received the error message

Can you show us the path where this TM is located? Is it cloud-based?
Can you open this TM in the "Translation Memories" view?

Stephane Picault said:

I stored the TM file in a folder next to the folder containing the project.

What do you mean by "a folder next to..."?

Stephane Picault 

To make sure Studio does not try to open a pre-configured TM that is not available any more, delete this file as already suggested:

C:\Users\%UserName%\AppData\Local\SDL\SDL Trados Studio\14.0.0.0

where %UserName" is your Windows user name.

Do this with Studio closed and restart Studio afterwards.
If you don't see this folder, follow the steps described in this KB article:
"The translation memory data file is corrupt" error message appears when starting Trados Studio or changing to the Translation Memories view (sdl.com)