Translation Memory

Hi - I've just purchased the new 2017 sdl studio tool. I have opened a TM (previously used with 2011) but there seems to be no coordination between the file open in editor and the TM - I have entire segments which I know I have translated before but there is no concordance when I open them. The only way I can find the translation is by running a search in TM. Why are the two not working together? I have also checked in settings and the file appears to be enabled as usual. 

Anyone any ideas ?

thanks 

Mairi-Claire