I’ve had great results from most attempts so far but I have taken a few extra steps to figure out what Cubase likes.
One of the things I’ve tried with hoplessly mushy old cassette tapes and old sketches was I imported the audio file into Cubase, created a Track and then made a copy of it. I used audio processing EQ to find some low thuds most often kick drums and some rhythmic treble noises and the rest I squeezed down to almost inaudible. Then I used the tempo detection tool on that horrible sounding track and in an overwhelming majority of cases it worked! Now I had a Tempo Track so I could delete the EQed Track and listen to the Metronome and the original sound file!
And I should note that I’ve also used Tempo Detection on just guitar sketches without problem whatsoever. Even funny time signatures are doable since the result is always in the somewhat suspicious time signature of 1/4. 
Does’t matter to too much. I can adjust that afterwards. 