Speculator, as with Validator, looks for TrackMaster data files on a fixed folder named c:\trkmast. If you're exporting those files from RDSS, that's the default export folder used.
If you're running Spec in DOS, or in Windows XP (or some normal environment which can run natively those older DOS programs), you likely have Spec installed in folder c:\spec160 (or whatever flavour of Speculator you use). In this case, you can just look in folder c:\trkmast to see if you indeed have the file there which you are telling Speculator to look for. If the card file is not there, put it there
If however, you are using a DOS emulation environment environment like Dosbox, perhaps running in Windows 10 (which if you are BTW, would have been nice to mention) -- then typically you 'mount' your local Speculator folder (say, c:\spec160) as a Drive volume. For example, in Dosbox: mount c: c:\spec160. Now you address Speculator as being in the root folder of Drive C within Dosbox.
HOWEVER - in this setup, since Speculator looks for TrackMaster data files in c:\trkmast, you must actually place your TrackMaster data files in the folder c:\spec160\trkmast, which to Speculator running in Dosbox Drive C, will look like c:\trkmast.
Ta da!
If Dosbox is not involved, well - try to double check you are specifying the correct folder location and card files you thought you did. That's all I got, so far.
Ted