I'm a newbie to Trados SDL 2017 and I've got a problem with the language pairs function for the creation of a new TM

I'm studying from the manual ' Getting Started' I want to create a new TM's with the language pair English/ German.  Unfortunately, the TL  choice doesn't offer me, German. My choice of both SL and TL is limited to only It- Dutch- English and French. Incidentally, these are my working languages that I recall to have selected when installing the programme on my computer. I went to the file tab and looked in the user section but couldn't find anything that would help me to re-install German as a choice. I'm not sure what to search for, I must admit that I'm lost. Any help would be much appreciated.